Add cmake build system

Add cmake support for CLC and ll asm language,
the latter includes clang preprocessing stage.
Add ctests to check for external function calls.

v2: fix typos, style

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Acked-by: Aaron Watry <awatry@gmail.com>
Tested-by: Aaron Watry <awatry@gmail.com>
Acked-by: Vedran Miletić <vedran@miletic.net>
llvm-svn: 347667