[kernel] Let objects inherit caps from superclasses

The main point of this change is to allow "global" capabilities defined
on the base object type. The example here is the clone capability on all
objects, which governs the ability to clone a handle.

Related changes in this commit:
- Renamed `kobject` to `object` as far as the syscall interface is
  concerned. `kobject` is the cname, but j6_cap_kobject_clone feels
  clunky.
- The above change made me realize that the "object <type>" syntax for
  specifying object references was also clunky, so now it's "ref <type>"
- Having to add `.object` on everywhere to access objects in
  interface.exposes or object.super was cumbersome, so those properties
  now return object types directly, instead of ObjectRef.
- syscall_verify.cpp.cog now generates code to check capabilities on
  handles if they're specified in the definition, even when not passing
  an object to the implementation function.

definitions/objects/channel.def

@@ -1,4 +1,4 @@
-object channel : kobject {
+object channel : object {
     uid 3ea38b96aa0e54c8
 
     capabilities [

definitions/objects/endpoint.def

@@ -1,7 +1,7 @@
 # Channels are objects that enable synchronous IPC of
 # arbitrary-sized messages.
 
-object endpoint : kobject {
+object endpoint : object {
     uid c5882f24a4c03b7e
 
     capabilities [

definitions/objects/event.def

@@ -0,0 +1,4 @@
+object event : object {
+    uid f441e03da5516b1a
+}
+

definitions/objects/mailbox.def

@@ -1,5 +1,4 @@
 # Mailboxes are objects that enable asynchronous IPC via event notification.
-# This is a second line of documentation
 
 object mailbox {
     uid 99934ad04ece1e07
@@ -11,7 +10,7 @@ object mailbox {
 
     method bind {
         param index uint
-        param source object kobject
+        param source ref object
         param event uint
     }
 

definitions/objects/object.def

@@ -1,6 +1,11 @@
 # The base type of all kernel-exposed objects
-object kobject [virtual] {
+object object [virtual] {
     uid 667f61fb2cd57bb4
+    cname kobject
+
+    capabilities [
+        clone
+    ]
 
     # Get the internal kernel object id of an object
     method koid {
@@ -17,9 +22,9 @@ object kobject [virtual] {
     # Block the current thread waiting for an one of multiple
     # objects to assert one of a set of signals
     method wait_many [static] {
-        param handles object kobject [list] # The objects to wait on
-        param mask uint64 # Bitmap of which signals to wait for
-        param handle object kobject [out] # Returns the object that signalled
-        param signals uint64 [out] # Returns the state of the signals
+        param handles ref object [list] # The objects to wait on
+        param mask uint64               # Bitmap of which signals to wait for
+        param handle ref object [out]   # Returns the object that signalled
+        param signals uint64 [out]      # Returns the state of the signals
     }
 }

definitions/objects/process.def

@@ -1,9 +1,9 @@
-import "objects/kobject.def"
+import "objects/object.def"
 
 # Processes are a collection of handles and a virtual memory
 # space inside which threads are run.
 
-object process : kobject {
+object process : object {
     uid 0c69ee0b7502ba31
 
     capabilities [
@@ -25,7 +25,7 @@ object process : kobject {
     # Give the given process a handle that points to the same
     # object as the specified handle.
     method give_handle {
-        param target object kobject [handle]           # A handle in the caller process to send
-        param received object kobject [out optional]  # The handle as the recipient will see it
+        param target ref object [handle]          # A handle in the caller process to send
+        param received ref object [out optional]  # The handle as the recipient will see it
     }
 }

definitions/objects/system.def

@@ -3,7 +3,7 @@ import "objects/vma.def"
 
 # The system object represents a handle to kernel functionality
 # needed by drivers and other priviledged services
-object system : kobject {
+object system : object {
     uid fa72506a2cf71a30
 
     capabilities [
@@ -21,17 +21,17 @@ object system : kobject {
     # Ask the kernel to send this process messages whenever
     # the given IRQ fires
     method bind_irq [cap:bind_irq] {
-        param dest object endpoint  # Endpoint that will receive messages
-        param irq uint              # IRQ number to bind
+        param dest ref endpoint  # Endpoint that will receive messages
+        param irq uint           # IRQ number to bind
     }
 
     # Create a VMA and map an area of physical memory into it,
     # also mapping that VMA into the current process
     method map_phys [cap:map_phys] {
-        param area object vma [out] # Receives a handle to the VMA created
-        param phys address          # The physical address of the area
-        param size size             # Size of the area, in pages
-        param flags uint32          # Flags to apply to the created VMA
+        param area ref vma [out] # Receives a handle to the VMA created
+        param phys address       # The physical address of the area
+        param size size          # Size of the area, in pages
+        param flags uint32       # Flags to apply to the created VMA
     }
 
     # Request the kernel change the IOPL for this process. The only values

definitions/objects/thread.def

@@ -1,4 +1,4 @@
-object thread : kobject {
+object thread : object {
     uid 11f23e593d5761bd
 
     capabilities [
@@ -6,7 +6,7 @@ object thread : kobject {
     ]
 
     method create [constructor] {
-        param process object process [cap:create_thread]
+        param process ref process [cap:create_thread]
         param stack_top address
         param entrypoint address
     }

definitions/objects/vma.def

@@ -1,6 +1,6 @@
 import "objects/process.def"
 
-object vma : kobject {
+object vma : object {
     uid d6a12b63b3ed3937
     cname vm_area
 
@@ -22,12 +22,12 @@ object vma : kobject {
     }
 
     method map [cap:map] {
-        param process object process
+        param process ref process
         param address address
     }
 
     method unmap [cap:unmap] {
-        param process object process
+        param process ref process
     }
 
     method resize [cap:resize] {