[kernel] Pass objects not handles to syscall impls

This commit contains a couple large, interdependent changes:

- In preparation for capability checking, the _syscall_verify_*
  functions now load most handles passed in, and verify that they exist
  and are of the correct type. Lists and out-handles are not converted
  to objects.
- Also in preparation for capability checking, the internal
  representation of handles has changed. j6_handle_t is now 32 bits, and
  a new j6_cap_t (also 32 bits) is added. Handles of a process are now a
  util::map<j6_handle_t, handle> where handle is a new struct containing
  the id, capabilities, and object pointer.
- The kernel object definition DSL gained a few changes to support auto
  generating the handle -> object conversion in the _syscall_verify_*
  functions, mostly knowing the object type, and an optional "cname"
  attribute on objects where their names differ from C++ code.
  (Specifically vma/vm_area)
- Kernel object code and other code under kernel/objects is now in a new
  obj:: namespace, because fuck you <cstdlib> for putting "system" in
  the global namespace. Why even have that header then?
- Kernel object types constructed with the construct_handle helper now
  have a creation_caps static member to declare what capabilities a
  newly created object's handle should have.

src/kernel/syscalls/system.cpp

@@ -14,8 +14,12 @@
 
 extern log::logger &g_logger;
 
+using namespace obj;
+
 namespace syscalls {
 
+using system = class ::system;
+
 j6_status_t
 log(const char *message)
 {
@@ -33,7 +37,7 @@ noop()
 }
 
 j6_status_t
-system_get_log(j6_handle_t sys, void *buffer, size_t *buffer_len)
+system_get_log(system *self, void *buffer, size_t *buffer_len)
 {
     // Buffer is marked optional, but we need the length, and if length > 0,
     // buffer is not optional.
@@ -43,25 +47,22 @@ system_get_log(j6_handle_t sys, void *buffer, size_t *buffer_len)
     size_t orig_size = *buffer_len;
     *buffer_len = g_logger.get_entry(buffer, *buffer_len);
     if (!g_logger.has_log())
-        system::get().deassert_signal(j6_signal_system_has_log);
+        self->deassert_signal(j6_signal_system_has_log);
 
     return (*buffer_len > orig_size) ? j6_err_insufficient : j6_status_ok;
 }
 
 j6_status_t
-system_bind_irq(j6_handle_t sys, j6_handle_t endp, unsigned irq)
+system_bind_irq(system *self, endpoint *endp, unsigned irq)
 {
-    endpoint *e = get_handle<endpoint>(endp);
-    if (!e) return j6_err_invalid_arg;
-
-    if (device_manager::get().bind_irq(irq, e))
+    if (device_manager::get().bind_irq(irq, endp))
         return j6_status_ok;
 
     return j6_err_invalid_arg;
 }
 
 j6_status_t
-system_map_phys(j6_handle_t handle, j6_handle_t * area, uintptr_t phys, size_t size, uint32_t flags)
+system_map_phys(system *self, j6_handle_t * area, uintptr_t phys, size_t size, uint32_t flags)
 {
     // TODO: check to see if frames are already used? How would that collide with
     // the bootloader's allocated pages already being marked used?
@@ -75,7 +76,7 @@ system_map_phys(j6_handle_t handle, j6_handle_t * area, uintptr_t phys, size_t s
 }
 
 j6_status_t
-system_request_iopl(j6_handle_t handle, unsigned iopl)
+system_request_iopl(system *self, unsigned iopl)
 {
     if (iopl != 0 && iopl != 3)
         return j6_err_invalid_arg;