maintain music rate speed adjust after music has finished

Keeps things like BGA effect clocks consistent when music stops.
Merge pull request #251 from sigatrev/MusicSpeed

maintain music rate speed adjust after music has finished
added GetStylesForGame method
Merge branch 'GetStylesForGame' of https://github.com/sigatrev/stepmania
Changed GetStylesForGame to not traverse the list of styles twice.
Pretend I didn't forget the +1.
Changed RollingNumbers to not set NAN velocity.
Updated actordef.txt.
fix REALLY BAD TYPO in GradeDisplay:SetGrade Lua function.
this is dumb and I'm too lazy to find out who's REALLY to blame so I want to assume it's my fault, probably. If anyone wants to bother clearing my name, check the stepmania SVN history. I don't care enough :v
Changed GradeDisplay::SetGrade to print errors instead of segfaulting on unloaded actors.
A couple actor docs.
Changelog_SSCformat.txt said we were on v0.82, but Song.h said we were on v0.81... fix that.
also update FILE_CACHE_VERSION to regenerate cache for #PREVIEWVID tag (if it isn't already)
ifdef'ed out AddATIToList and RemoveATIFromList on WIN32 because they cause mapconv to crash.
Kyzentun: it's not your fault that our mapconv.exe is psychopathic
replace psychopathic mapconv.exe with one compiled by "g++ (rev5, Built by MinGW-W64 project) 4.8.1"
This is probably the part where someone says "why do we have the compiled binaries in the source tree anyways if they're just going to cause problems like this?"
fix ScreenGameplaySyncMachine crash

was not setting steps to null, caused access violations
Merge pull request #255 from sigatrev/SyncMachine

fix ScreenGameplaySyncMachine crash
dear github: our travis build is broken in a pretty serious way (The command "sudo apt-get install libc6-dev" failed and exited with 100), and I know this isn't travis-support nor the right place for it but I thought I should let someone outside of IRC know the reason for it thanks
Added NoteSkinManager::GetDefaultNoteSkinName so that PlayerOptions can avoid clearing the noteskin when the clearall mod is used.
Merge pull request #256 from kyzentun/NoteskinClearFix

Fix crash when "clearall" is used.
Didn't realize RollingNumbers was supposed to have negative velocity.