[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.

scripts/definitions/transformer.py

@@ -1,11 +1,12 @@
 from .parser import Transformer, v_args
 
 def get_opts(args):
-    from .types import Description, Options, Type, UID
+    from .types import CName, Description, Options, Type, UID
 
     kinds = {
         Description: "desc",
         Options: "opts",
+        CName: "cname",
         UID: "uid",
         Type: "typename",
     }
@@ -89,6 +90,11 @@ class DefTransformer(Transformer):
     def uid(self, s):
         return s
 
+    @v_args(inline=True)
+    def cname(self, s):
+        from .types import CName
+        return CName(s)
+
     @v_args(inline=True)
     def name(self, s):
         return s