[project] Generate syscalls from new interface DSL

This change adds a new interface DSL for specifying objects (with
methods) and interfaces (that expose objects, and optionally have their
own methods).

Significant changes:

- Add the new scripts/definitions Python module to parse the DSL
- Add the new definitions directory containing DSL definition files
- Use cog to generate syscall-related code in kernel and libj6
- Unify ordering of pointer + length pairs in interfaces

definitions/objects/vma.def

@@ -0,0 +1,29 @@
+import "objects/process.def"
+
+object vma : kobject {
+    uid d6a12b63b3ed3937
+
+    method create [constructor] {
+        param size size
+        param flags uint32
+    }
+
+    method create_map [constructor] {
+        param size size
+        param address address
+        param flags uint32
+    }
+
+    method map {
+        param process object process
+        param address address
+    }
+
+    method unmap {
+        param process object process
+    }
+
+    method resize {
+        param size size [inout]
+    }
+}