cproc (small C11 compiler based on QBE)

cproc is a C11 compiler using QBE as a backend. It is released under
the ISC license. Some C23 features and GNU C extensions are also
implemented. There is still much to do, but it currently implements
most of the language and is capable of building software including
itself, mcpp, gcc 4.7, binutils, and more.

This doesn't support 32-bit x86. It supports x86_64 (tested) and
aarch64 (untested; if it doesn't work, send me a patch and I'll
include it).

The build runs cproc's self-test suite. The results will be saved to:
  /usr/doc/cproc-$VERSION/check-results.txt
