Implement microphone pass-through in audio engine.

* No way to disable it, it even invades menus.
* Requires very low suggestedLatency (so some platforms are probably b0rked).
Merge branch 'master' into pass-through
Merge branch 'master' into pass-through

Conflicts:
	game/pitch.hh
Merge branch 'master' into pass-through
Reworked Song selector navigation.
- Hiscore always on, no separate mode for that
- Up/down traverse menu where left/right may browse songs, sort modes, type filters or info screens (also jukebox mode)
- New graphical layout is not done yet so the menu is invisible and hiscore display is somewhat b0rked
- Type filter only toggles vocals filter for now
Fix song type filtering (new style).
Minimal UI for the menu.
Make CMake find GDK-PixBuf in M cross environment.
SingStar XML parser fixed & cleanup:
- Do full parsing during song loading (so that tracks are detected properly)
- Fix default singer name in multitrack in one mode (Solo 1)
Added Portuguese (Brazil) translation.
Update docs with GitHub transition.
Merge pull request #1 from josephgbr/master

Translation to Portuguese (Brazil)
Remove some outdated docs (migrated to GitHub issue tracker or wiki).
Update authors file.
Remove man page for ss_ipu_decode (tool removed earlier), add gh_fsb_decode man page (previously missing from CMakeLists.txt).
Merge branch 'master' into pass-through
Fix whitespace in ss_chc_decode.cpp
Some pass-through refactoring and reduce volume ratio.
Option to toggle microphone pass-through.
Configurable pass-through volume ratio.