From Lars Roland: define an "installation" version of GTK+ 2.x and Pango

From Lars Roland: define an "installation" version of GTK+ 2.x and Pango
in "config.nmake", and use that in the NSIS script when generating the
NSIS installer, so it puts GTK+ and Pango in the appropriate
subdirectories.  Also, when uninstalling, remove both of the sets of
subdirectories.

As per his suggestion, get rid of the "GTK1_VERSION" and "GTK2_VERSION"
macros, and just directly insert the values where those macros were used
- "GTK1_VERSION" wasn't used at all, and "GTK2_VERSION" was only used
immediately below where it was defined, and stuff elsewhere, such as in
the NSIS script, didn't use them and would break if you changed them
anyway.

svn path=/trunk/; revision=10976