setup: Show error when server address not entered.

Don't launch the game if a server address has not been entered; show a
message to the user instead. This fixes #121.
pcsound: Fix resouce leak with speaker_handle.

speaker_handle should be close()d after forking the separate sound
server. This fixes #192 (thanks Edward-san).
sound: Fix crash with large values of snd_channels.

Sanity check the handles passed to the i_sdlsound.c API functions and
ignore requests that involve channel numbers higher than 15. This
fixes a crash if the user sets the snd_channels config variable is set
to a high value. This fixes #149 (thanks Alexandre Xavier).
midifile: Fix portability issue with malloc(0).

In the C standards, malloc(0) may return NULL without indicating a
failure to allocate. As values read from the MIDI file may be
arbitrary, add one to the allocated length so that we always allocated
a positive value. This fixes #165 (thanks nmain).
doom: Allow warp up to MAP40 to match Vanilla.

Vanilla Doom allows warp with the IDCLEV cheat up to MAP40, though it
normally crashes. Match this behavior and set MAP40 as the maximum
rather than MAP34. This fixes #181 (thanks Alexandre Xavier).
setup: Save selected game when browsing menus.

Once a game type (IWAD) has been selected, remember that selection
rather than resetting to the first item in the list when the window is
closed and reopened. This fixes #169 (thanks Alexandre Xavier).
Fix "fast doors make two closing sounds" and "fast doors reopening with wrong sound" engine bugs.
Merge branch 'master' of https://github.com/chocolate-doom/chocolate-doom

Conflicts:
	src/doom/st_stuff.c