manually map some seL4 typedefs to rust types
Replace some higher-level C typedefs that seL4 defines with specific rust types. Most importantly this maps seL4_Word to usize which isn't expressed by the C typedefs.
Replace some higher-level C typedefs that seL4 defines with specific rust types. Most importantly this maps seL4_Word to usize which isn't expressed by the C typedefs.