General purpose C FFI

[ViralBShah]

We need a general purpose FFI that can call any C library, using either tcc or clang.

Suggested interface:

loadc("libpcre") # loads the C library, reading headers and all
/* the namespace libpcre could be used to avoid naming clashes _/
pcre_compile("foo\s_bar", PCRE_CASELESS, ...)

[ViralBShah]

Duplicate of #259.

[StefanKarpinski]

Not exactly a dup, but same general idea.