Add experimental XBMC installation.
Add experimental darkplaces quake

Just darkplaces-rpi with shareware game file from id software. Runs nice if you run RetroPie/roms/ports/darkplacesquake.sh from console.  If it is run from emulationstation there are issues. Controls are different and the menu cannot be used. I don't know why, but there seems to be a problem between emulationstation2 and SDL/SDL2 games/emulators like mupen64plus-rpi and darkplaces quake.

Workaround: Run dark places as root atm (line 44).
darkplaces: minor improvements

-Set right config file permissions.
-Unzip without asking.
-Move game files from /roms/ports/id1 to more clear /roms/ports/quake/id1.
-Now the apt auto remove step no longer will wait for user input to remove packages (making the entire script fully automatic, this was the only place retropie_setup.sh stopped for me along the way)
Merge pull request #503 from free5ty1e/bugfix/apt-autoremove-step-no-longer-requires-prompt

-Now the apt auto remove step no longer will wait for user input to remo...
Added PNG library to dependencies pf module psxlibretro
Added library libx11-dev to psxlibretro module
Add experimental fmsx-libretro core

According to this post (http://blog.petrockblock.com/forums/topic/use-the-libretro-msx-implementation/) the libretro core runs "great".
fmsx-libretro: remove platform defines

build error with platform=rpihardfloat.
Add experimental Atari Lynx libretrocore handy

It compiles and runs games.
fmsx-libretro: copy ROMs to BIOS folder
Added libsdl1.2-dev dependency for mame4all
Merge pull request #507 from bsilvereagle/master

Added libsdl1.2-dev dependency for mame4all
gpsp: add libsdl1.2-dev dependency

https://github.com/petrockblog/RetroPie-Setup/issues/504
Merge pull request #508 from gizmo98/patch-6

gpsp: add libsdl1.2-dev dependency
Merge pull request #506 from gizmo98/patch-4

Add experimental Atari Lynx libretrocore handy
Merge pull request #505 from gizmo98/patch-3

Add experimental fmsx-libretro core
Merge pull request #491 from gizmo98/patch-1

Add experimental darkplaces quake
Merge pull request #475 from gizmo98/patch-5

Add experimental XBMC installation.
mame4all: Try to fix compilation issue

Just add the missing libs (https://github.com/petrockblog/RetroPie-Setup/issues/509) and use the same -march CFLAG as RetroPie-Setup.