Instrumentation hook handler functions are hardcoded for 64-bit

[kkysen]

The handler functions in analysis/runtime/src/handlers.rs for the hooked allocator functions are currently hardcoded for 64-bit systems, namely

malloc:

c2rust/analysis/runtime/src/handlers.rs

Line 5 in 88accbd

pub fn malloc(mir_loc: MirLocId, size: u64, ptr: usize) {

calloc:

c2rust/analysis/runtime/src/handlers.rs

Line 22 in 88accbd

pub fn calloc(mir_loc: MirLocId, nmemb: u64, size: u64, ptr: usize) {

realloc:

c2rust/analysis/runtime/src/handlers.rs

Line 32 in 88accbd

pub fn realloc(mir_loc: MirLocId, old_ptr: usize, size: u64, new_ptr: usize) {

reallocarray:

c2rust/analysis/runtime/src/handlers.rs

Line 46 in 88accbd

pub fn reallocarray(mir_loc: MirLocId, old_ptr: usize, nmemb: u64, size: u64, new_ptr: usize) {

These functions match the c2rust transpiled malloc, calloc, realloc, reallocarray on 64-bit systems, but c2rust transpile hardcodes size_t as libc::c_ulong, which (usually, not on Windows) is u64, rather than using the platform-independent libc::size_t/usize. This is something we'd like to fix in c2rust transpile (#259, #305), but at least for that you could re-transpile on different platforms. We can't do that for c2rust_analysis_rt, though, so we should match the platform-independent way libc translates these functions, using libc::size_t.