[ccache] Patch: Xcode compatibility

[Sean Gies]

Here's a patch I created so that I can use ccache with Apple's Xcode 
IDE.

1. Added more extensions to better support Objective-C and 
Objective-C++.

2. Added a check to the argument processing logic to handle this sort 
of invocation:
	/usr/share/bin/ccache /usr/bin/distcc /usr/bin/gcc-3.3 ...

In order to handle multiple compiler versions, Xcode uses full paths to 
invoke an explicit version of distcc or gcc.  This confused ccache 
because it thought the gcc-3.3 argument to distcc was a source file.

-Sean