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.

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

Add mem* functions to stdio
Add constant int functions

The sigaction struct should not be a typedef, but the sigset_t struct
should be a typedef.

Dan Robertson authored 7 years ago and Dan Robertson committed 7 years ago

Create stubs for signal.h

Add a crate with stubbed functions for the float.h header.

Add implementations of sprintf and snprintf so that we can get a bit
closer to compiling libc-test.

The current implementation of open requires the user to pass all three
args to the function. It should use a va_list and allow a user to
provide only the filename and flags.