Stop searching gcc dirs for C compiler headers

Heads up,

I just committed this patch:
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20090216/012615.html

This changes clang to stop searching for the GCC versions of "float.h" and friends. In theory, all of these headers are implemented and I think that clang should find them ('make test' passes at least). However, there is always some possibility of breakage. If you see any, please let me know. Also, as a workaround, you can define system header search paths with the CPATH or C_INCLUDE_PATH environment variables.

The motivation for doing this is that the GCC GPL2 header files have a license clause which states "this file is GPL unless you compile it with GCC". Since Clang is not GCC, this implicitly makes all programs compiled with Clang GPL that use these. This is "bad", and our versions of the headers are now feature complete, so it is time to sever this tie.

Please let me know if you notice any problems. With luck, you won't notice any change! :slight_smile:

-Chris