Added (possibly non-optimal, but working) support for the CDECL calling convention

[ForceBru]

This code may be a bit messy (because I modified it to emit 32-bit assembly instead of 64-bit), but the main features are the following:

• CDECL calling convention instead of passing functions' arguments in registers
• if there are no free registers available in asm_gen.py, this uses the stack for local variables instead

Again, the code was modified to emit 32-bit assembly only, so some changes need not be merged into the master branch.

[ForceBru]

BTW, ShivyC to compile C into assembly plus pycca to assemble it plus PyVM to run the generated binary do work, so right now, with your awesome C compiler, one can run C code through pure Python!