opl additive voice volume calculation fix

opl additive voice volume calculation fix
opl note limitation and octave overflow fixes
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.
Merge branch 'master' of github.com:chocolate-doom/chocolate-doom
Merge pull request #465 from khokh2001/opl-fix

opl additive voice volume calculation fix

Adjust how the OPL volume register values are calculated based on the
channel, note and global MIDI volume, to better match how the Doom
DMX library performs these calculations (thanks Alexey Khokholov /
khokh2001).
Merge pull request #466 from khokh2001/opl-fix2

opl note limitation and octave overflow fixes

Adjust how the OPL MIDI code behaves at extreme MIDI note values
(high/low octaves) to better match how the Doom DMX library decides
on the OPL register value (thanks Alexey Khokholov / khokh20010.
opl: Fix code style to match guidelines.

Eliminate tab characters and trailing whitespace. Add extra
whitespace around operators in for() expressions.
setup: Fix bug with strdup() of NULL pointer.

getenv() can return NULL if the environment variable is not set, but
the result of getenv() was always being passed to M_StringDuplicate()
without any check. This could cause crashes on some platforms.
Instead, rework the code into a first stage that gets the player's
name and a second that duplicates it into a mutable form.

This fixes #455.
Merge pull request #3 from chocolate-doom/master

Sync with upstream