Update toolchain

See merge request redox-os/relibc!338

This also replaces all the assembly that previously used the AT&T style
with the (in my opinion) superior Intel syntax.

I tried prepending `.att_syntax prefix`, but that did not work...

Simplify gmtime_r() day-of-year calculation, correct comment

See merge request redox-os/relibc!311

Centralize page size info in platform abstraction

See merge request redox-os/relibc!334

Handle TCSETSW and TCSETSF in ioctl

Closes #168

See merge request redox-os/relibc!324

Convert test runner to rust

See merge request redox-os/relibc!333

Use as-less cast for UTC string

See merge request redox-os/relibc!331

Test for time.h constants

See merge request redox-os/relibc!332

Use BufWriter (instead of LineWriter) for FILEs other than stdout and stderr

See merge request redox-os/relibc!328

aarch64: TLS arch_read implementation

See merge request redox-os/relibc!330

Change ld.so linker script file name for x86_64 Linux to fix compilation issue

See merge request redox-os/relibc!329

BufWriter has more capacity (8k vs 1k) and doesn't flush the stream after '\n'.
That change helps to reduce the number of syscalls, especially when dealing with text files.

Since BufWriter has a different way of getting number of pending elements than LineWriter -
Pending trait was introduced to deal with that.