GTK3 bundle fixups.

gtk3-obs.autopackage:
Move the etc and share stanzas into the file stanza. Don't package the HTML documentation. Add the .pc files (unmodified for now).

bundle-gtk3.ps1:
Turn on verbosity when generating packages (for now). Don't create batch redirects for our executables.

.gitmodules:
Use a Gitextensions-compatible name for the download-mingw-rpm submodule.