drop -uninstalled.pc files
These were meant to provide the ability to use GLib directly out of its
build tree but have a couple of rather serious limitations that prevent
their serious use:
- these files only worked with programs built using libtool
- for non-trivial uses, other environment variables will need to be
setup to allow GLib to function properly
- the system doesn't stack well when attempting to use multiple
libraries all uninstalled
The jhbuild --prefix= style system works much better in every way, so we
remove this old hack.