Make std.file.chdir safe
Call cenforce in one line
Don't use built-in .sort in std.string.abbrev()

This also makes it CTFE-able. Yay!
Merge pull request #2558 from tom-tan/safe-file-chdir

Make std.file.chdir safe
Fix issue 13535 byCodeUnit doesn't satisfy hasSlicing
Merge pull request #2559 from quickfur/abbrev_sort

Don't use built-in .sort in std.string.abbrev()
Merge pull request #2563 from sinkuu/bycodeunit_slice

Fix issue 13535 byCodeUnit doesn't satisfy hasSlicing
Fill in ARM FPSCR stub
Merge pull request #2564 from ibuclaw/armfpscr

Fill in ARM FPSCR stub in std.math