[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

src/kernel/vm_space.cpp

@@ -286,7 +286,7 @@ vm_space::handle_fault(uintptr_t addr, fault_type fault)
 }
 
 size_t
-vm_space::copy(vm_space &source, vm_space &dest, void *from, void *to, size_t length)
+vm_space::copy(vm_space &source, vm_space &dest, const void *from, void *to, size_t length)
 {
     uintptr_t ifrom = reinterpret_cast<uintptr_t>(from);
     uintptr_t ito = reinterpret_cast<uintptr_t>(to);