Relocating Fedora's RPM database

The pattern where there's a compiled summary/cache/more-efficient-form for multiple files (like GSettings schemas glib-2.0/schemas/*.xml being summarized in gschemas.compiled) is useful if at least one of these is true:

* the files being summarized are in a format that is relatively costly to parse, compared with the number of programs that will want to parse it, so updating a summary during package management operations is cheaper than reading the source files from first principles every time (like schema XML)
* there are lots of files and many programs will want to load all of them, so reading the summary requires fewer syscalls and fewer disk seeks than reading the source files (like icons and fonts)
* the name of the correct file to open to get a particular "interface" is not immediately obvious unless you can look it up in the summary (like fonts, which have no obvious relationship between font name and filename)

None of those apply to GObject-Introspection: if a Python or JS program wants to use a GTK 3 UI, then it should already know (hard-coded in its source code) that it wants the Gtk typelib, API version 3.0, so it can load Gtk-3.0.typelib without needing to look it up in a summary. Typelibs are a binary format like a shared library, so the caller doesn't need to parse something like XML.