rename _improper_ctypes_check functions

[Freax13]

rustc seems to have added a warning for dupplicate extern functions with different signatures:

warning: `_improper_ctypes_check` redeclared with a different signature
   --> src/bootinfo/mod.rs:119:5
    |
119 |     fn _improper_ctypes_check(_boot_info: BootInfo);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
    | 
   ::: src/bootinfo/memory_map.rs:235:5
    |
235 |     fn _improper_ctypes_check(_boot_info: MemoryMap);
    |     ------------------------------------------------- `_improper_ctypes_check` previously declared here
    |
    = note: `#[warn(clashing_extern_decl)]` on by default
    = note: expected `unsafe extern "C" fn(bootinfo::memory_map::MemoryMap)`
               found `unsafe extern "C" fn(bootinfo::BootInfo)`

this pr simply renames the functions to get rid of the warning

[phil-opp]

Thank you!

[phil-opp]

Published as version 0.9.5.