Add compiler option to list all dependent files for a glsl input

[GoogleCodeExporter]

It would be nice to be able to list all of the glsllib files included for a 
given input. Build systems can use this to then do dependency 
tracking/caching/etc. The compiler can hopefully get this information rather 
easily, where as doing it externally would require parsing all of the files. As 
the compiler inputs get more complex (with preprocessor logic/etc) it gets more 
difficult to do this from the outside.

e.g.,
glsl-compiler --input=foo.glsl --list-dependencies
foo.glsl
somelib.glsllib
some/path/lib.glslib
...

If dumped on stdout it'd be possible to grab this and pipe it to another file 
or programmatically act on it.

Original issue reported on code.google.com by benvanik@google.com on 17 Feb 2012 at 10:24