Simplify an ifdef

We don't need to check both platform and compiler at the same time,
checking the compiler is enough here.
Remove excludes of nonexistent files
Remove an unused function wrapping a standard function

This allows removing a whole file.
Remove an MSVC resource editor state file

This file contains the local UI state of the resource editor,
and should not be committed to version control.
Merge pull request #200 from mstorsjo/minor-cleanups

Minor cleanups