Revert openlibm install script

See merge request redox-os/relibc!143

Turns out that this only worked because I didn't clean before rebuilding, so it still had access to the old files. Sorry.

Fix openlibm & fenv and add more integer types

See merge request !141

Reuse musl's setjmp implementation

See merge request !139

Install openlibm from Makefile

See merge request !138

Fix undefined behavior

See merge request !137

Transmuting from an immutable to a mutable reference is undefined
behavior in Rust, with the exception of UnsafeCell which tells the
optimizer to not draw too many conclusions. Sadly UnsafeCell::get cannot
yet be used in statics (see https://github.com/rust-lang/rust/issues/51718),
so this works around that by making the statics into functions and
making C macros to call those.

Add empty locale functions

See merge request !135

Add scanf

See merge request !134

sys_wait: implement C macros properly

See merge request !133

Remove the broken Rust functions and instead provide C macros in a
`include/bits` header. The C macros were taken from musl.

Fix compilation error in `sys_wait`

See merge request !132

Add `sys_wait` functions (Fixes #81)

Closes #81

See merge request !131

Update `platform::rawfile`

Make functions taking raw pointer return &'a instead of &'static

Simplify cstr_from_bytes_with_nul_unchecked()