Add gamepad config for PS4 DualShock 4.

Thanks to Matt Davis (3nT) for providing a detailed report for this
gamepad.
Merge branch 'master' of github.com:chocolate-doom/chocolate-doom
Rogue fixed DOOM bug regarding switch sound origins

Re-examination of assembly reveals use of &line->frontsector->soundorg
instead of buttonlist->soundorg.
Another teleport beacon correction

Flag to be cleared is MF_SPECIAL, not MF_SOLID (verified against
disassembly). Otherwise you get to spawn an infinite number of rebels
from one beacon. Not to mention, it isn't SOLID to start with.
Missed change for startskill init

Resolves #433
Default screenblocks 10, not 9

Resolves #196
setup: dynamically set size of iwad_labels array

With the addition of the Freedoom IWADs, the number of IWADs supported
by chocolate-doom has been raised to 10. However, the iwad_labels[]
array only holds place for up to 8 pointers. Incidently, I have all 10
IWADs installed and trying to warp into a game from
chocolate-doom-setup leads to an out-of-bounds access of this array
and so the application crashes with a segmentation fault.

Instead of increasing the array size to 10, which will bite us next
time, I decided to set its size dynamically as soon as the number of
IWADs of known.
opl additive voice volume calculation fix

opl additive voice volume calculation fix
opl note limitation and octave overflow fixes
opl drum note fix

fixed note drum instrument should be 60
opl voice allocation fix

opl voice allocation fix when there are no free voices
Merge pull request #467 from khokh2001/opl-fix3

Use MIDI note number 60 for percussion instruments, unless overridden
by the fixed_note field in the GENMIDI lump.
Merge pull request #468 from khokh2001/opl-fix4

Fix voice allocation when there are no more free voices. This fixes a
long-standing (but minor) discrepancy between the OPL code and the DMX 
library that was marked in the code with a TODO.
Update i_oplmusic.c
opl additive voice volume calculation fix

opl additive voice volume calculation fix
Automap accuracy fixes

* Grid is not supported and gives no such message
* Spot marking behavior is substantially different
Revert "Automap accuracy fixes"

This reverts commit 12ecb4550e46ffdc28248be185738a88be033afd.
Automap accuracy fixes (against proper game)

* Grid is not supported and gives no such message
* Spot marking is substantially different
Remove unreferenced "grid" variable

And yes I double checked the commit target this time.
opl: Internally swap MUS/MID percussion channel #s.

MIDI uses channel 9 for percussion but MUS uses channel 15. As the
channel numbers matter when we run out of free voices (#468),
internally swap channels 9 and 15 so that channel precedence is
decided correctly.