Allow the user to specify that they want static libraries through the
--{enable,disable}-{static,shared} switches like libtool. The mesa build
only allows for one at a time, so static will be chosen if someone has
passed --enable-static or --disable-shared.

This also allows the mklib options to be set at build time. This allows
-static to be set for mklib, but any platform specific settings are
allowed by setting MKLIB_OPTIONS for configure.

Handling of the program libraries through the APP_LIB_DEPS variable is
pretty ugly, but it seems to work.