Release 1.0.2 last SDL1-based version

This is intended as a checkpoint release (consolidating various bugfixes etc. since the last release) but most importantly this is the 'last official SDL1-based version of the Dave Gnukem 1 source code' before we make a big jump to integrate Matteo Bini's valuable (independently developed) implementation of SDL2 support:

#135 (Thanks to Matteo Bini for this - who is also working on Debian support and Debian packaging and other contributions)

So for any downstream ports that might want or need to stick to SDL1 for some reason at this, you may want to use this release or git head for this release, though it's recommended for ports to please try update to SDL2 also, as SDL1 is very old at this point and SDL2 is better supported (and brings other potential advantages for gamedev).

Related issue to also formally discuss upcoming SDL2 support in next release:
#140