built in import c header files

[Walter Bright]

There's another huge problem with C files.

It's the predefined macros. Every compiler generates a different set of them, 
and in each compiler the set varies by compiler version, target, switch 
settings, etc.

Most are undocumented.

I think gcc has somewhere near a thousand of them.

Naturally, every non-trivial C program winds up totally dependent on them.