Improve infrastructure.

Do more encapsulation of raw pointers, use more PrimaryMaps instead of
Vecs, add a table.rs for managing table storage.

lib/execute/src/mmap.rs

@@ -16,6 +16,7 @@ fn round_up_to_page_size(size: usize, page_size: usize) -> usize {
 
 /// A simple struct consisting of a page-aligned pointer to page-aligned
 /// and initially-zeroed memory and a length.
+#[derive(Debug)]
 pub struct Mmap {
     ptr: *mut u8,
     len: usize,