Thanks to Pau Garcia i Quiles for the inspiration for the patch.
I've tweaked it a bit compared to what's in the bug tracker: this
commit does not allow empty global variable names.
I also added usage of the new feature to an existing test. Although
it has no effect on the resulting Visual Studio projects, you can
verify that the VSResource test produces a non-empty globals section
in the generated .vcproj(x) files.
To get rc defines to work in the VS10 IDE requires \" when
constructing PreprocessorDefinitions strings. This is different
than defines for cl.
Also, per-file rc defines were not being generated. Fix that, too.
