Fixed: Compiler warnings

Unused variables and tautological conditions.
Started work branch for separating the UI framework in a shared lib

The client's UI framework has grown large enough to warrant moving
it into its own shared library called "libappfw" (deng_appfw).

Going forward, this'll ensure proper decoupling between the UI and
the rest of the client.

Todo: Move and update relevant sources.
Refactor: Continued setting up libappfw and updating the client
Refactor: Updating client to use libappfw
Refactor|Client: Updated to use libappfw

The generic portions of the UI framework have now been migrated to
libappfw.
Windows|Installer: Deploy deng_appfw.dll
Merge branch 'libappfw'
Refactor|libdeng1: Renamed the "boolean" define to "dd_bool"

Windows system headers define a "boolean" with a different size. To
avoid this conflict, libdeng1's boolean is now dd_bool. Naturally this
only has relevance for old/C code.

Also fixed some issues remaining from the libappfw migration.