Allow for PNG screenshots.
Add some strictly unnecessary curly braces.
Remove 0 summand.
Add PNG screenshots to advanced video options menu.
Merge pull request #361 from fabiangreffrath/png_screenshots

Allow for PNG screenshots.
Add a dedicated key for taking screenshots.
Initialize key_menu_screenshot with -1.
Print a warning if the user is attempting to record or playback a demo or connect to a network game using one of the BFG Edition IWADs.
Merge pull request #364 from fabiangreffrath/key_screenshot

Add a dedicated key for taking screenshots.
Remove superfluous dividers.
Merge pull request #365 from fabiangreffrath/bfg_warning

Print a warning if the user is attempting to record or playback a demo o...
heretic/hexen: Fix automap background scrolling.

There was a bug where it was possible to keep moving the background
when the boundaries of the map were reached. This is because the code
to move the background was done in calls to AM_Drawer(), which is
fundamentally a bad idea. Some old commented-out code shows that this
was previously done in AM_Drawer (same location that scrolls the map
itself), but it was moved. Move it back.

Thanks to Chris Fielder for the bug report; this fixes #321.
sound: Add config variable to control buffer size.

Add snd_maxslicetime_ms variable to control the size of the output
sound buffer, and reduce the default from 70ms to 28ms to match Doom's
35fps timer. Thanks to Holering for reporting this (fixes #345).
music: Add config var for external music program.

Mix_SetMusicCMD() allows a program to be specified to configure an
external program to be invoked for music playback. Add a config
variable (snd_musiccmd) to allow this to be set from a configuration
file. Thanks to Holering for his comments on Doomworld about how to do
this.
setup: Add missing snd_maxslicetime_ms variable.

Preserve the snd_maxslicetime_ms variable when loading/saving configs
in the setup tool.
pcsound: Extend frequency table to 128 entries.

Extend from 96 to the full 128 entries found in the frequency table in
the Vanilla .exes. This was helpfully posted by Gez to the Doom wiki:

  http://doomwiki.org/wiki/Talk:PC_speaker_sound_effects

Change from the current scheme of storing frequency values to using
the timer divisor values used by the Vanilla .exes; divide into the PC
timer frequency to calculate the frequencies to play.

Thanks to Gez for dumping the full list of frequencies; this fixes #336.
doom: Emulate 'no fog on spawn west' Vanilla bug.

A deathmatch player spawning facing directly west does not see the
normal teleport fog (or hear it). This is because of an angle that
should be unsigned but is actually signed. Import PrBoom's code to
emulate this bug. This fixes #186.
doom: Add initial support for versions < v1.9.

Add -gameversion options for v1.666, v1.7, v1.8. Set demo and savegame
headers appropriately depending on version. Also add an enum entry for
Doom v1.2 but no code support for it yet.
heretic/hexen: Fix -timedemo.

The -timedemo flag is broken in Vanilla Heretic/Hexen, as not all
fields are read from the demo headers. Fix it, as there's no utility
in having it nonfunctional and plenty of utility in having it
functional. This fixes #300.
Set default for key_menu_screenshot to 0.

In #364 I recommended -1 as the default to avoid taking screenshots in
some situations where a key event is posted for key 0. It turns out
that wasn't such a great idea, as -1 is not parsed properly by the
config parser, and is shown as ??-1 in the setup tool. Default to zero
instead, and add guards to prevent screenshots being taken by mistake.

Thanks to Alexandre-Xavier for pointing this out.