[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/device_manager.cpp

@@ -14,7 +14,7 @@
 #include "objects/endpoint.h"
 
 
-static endpoint * const ignore_endpoint = reinterpret_cast<endpoint*>(-1ull);
+static obj::endpoint * const ignore_endpoint = reinterpret_cast<obj::endpoint*>(-1ull);
 
 static const char expected_signature[] = "RSD PTR ";
 
@@ -380,7 +380,7 @@ device_manager::dispatch_irq(unsigned irq)
     if (irq >= m_irqs.count())
         return false;
 
-    endpoint *e = m_irqs[irq];
+    obj::endpoint *e = m_irqs[irq];
     if (!e || e == ignore_endpoint)
         return e == ignore_endpoint;
 
@@ -389,7 +389,7 @@ device_manager::dispatch_irq(unsigned irq)
 }
 
 bool
-device_manager::bind_irq(unsigned irq, endpoint *target)
+device_manager::bind_irq(unsigned irq, obj::endpoint *target)
 {
     // TODO: grow if under max size
     if (irq >= m_irqs.count())
@@ -400,7 +400,7 @@ device_manager::bind_irq(unsigned irq, endpoint *target)
 }
 
 void
-device_manager::unbind_irqs(endpoint *target)
+device_manager::unbind_irqs(obj::endpoint *target)
 {
     const size_t count = m_irqs.count();
     for (size_t i = 0; i < count; ++i) {