For AArch64, the ring crate depends on the presence of this header and a definition
of getauxval.

The pre-index operator ('!') was missing at the end of the stp
instruction.

As a result, the stack pointer wasn't updated after the
store of the 64-bit pair and the stored values were basically lost when
follow on code used the stack for later store ops.

tests: Macro based error handling

See merge request redox-os/relibc!195

Implement swab

See merge request !187

implements wcsrchr from wchar.h

See merge request !197

add calloc integer overflow check

See merge request !188

Change LONG_BIT definition, fixes #148

Closes #148

See merge request !198

Turns the results of these macros from compound to regular statements using the old `do { ... } while(0)` trick. Must have for function-like macros.

realpath: Fixing undefined behaviour in the second test. If the call fails the resolved_name argument cannot be used for error checking because its state is undefined by SUSv2.
pipe: Changing the order of close and write error handling code. Errors in close could overwrite errno after write errors, returning incorrect error messages.
gmtime: Removed duplicate checks
Other fixes for fseek, rename, mktime, putwchar

Implements wcscspn function from wchar.h

See merge request !196

This will allow us to redefine the exit function.

For example:
```
#define exit(code) { \
    fprintf(stderr, "%s:%d: exit(%s) in function ‘%s’\n",
        __FILE__, __LINE__, #code, __func__); \
    _exit(code); \
}
```

General test cleanups

See merge request redox-os/relibc!193

unistd: Generate correct C defines for PATH_SEPARATOR

See merge request redox-os/relibc!194

When the execution reaches the end of the main functions, they implicitly return a successful status.

tests: set C11, enable pedantic warnings, fix GCC and Clang warnings

See merge request redox-os/relibc!192

ctype: Implement _tolower, _toupper

See merge request redox-os/relibc!191

ctype: Add tests for toascii, tolower, toupper

See merge request redox-os/relibc!190

ctype: Fix iscntrl, isgraph, ispunct, make tests exhaustive

See merge request !189