[llvm-rc] Handle C preprocessor output

[llvm-rc] Handle C preprocessor output

When preprocessing resource scripts (which can easily be done outside
of llvm-rc), included headers can leave behind C declarations (despite
preprocessing with -DRC_INVOKED), that can't be parsed by a resource
compiler.

This is handled in all of rc.exe, by parsing the preprocessor output
line markers and ignoring content from files named *.h and *.c,
documented at [1].

In addition to this filtering, strip out any other preprocessor directive
that is left behind (like pragmas) which also can't be handled by the
tokenizer.

The added test uses both standard #line markers (supported by rc.exe) and
GNU style extended line markers, thus this test doesn't pass with rc.exe,
but passes with GNU windres. (Windres on the other hand doesn't filter
out files named *.c, only *.h.)

Differential Revision: https://reviews.llvm.org/D46579

[1] https://msdn.microsoft.com/en-us/library/windows/desktop/aa381033(v=vs.85).aspx

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331903 91177308-0d34-0410-b5e6-96231b3b80d8