Merge pull request #1 from rheit/master

- Added Blue Shadow's DropInventory ACS function.
- Added jpalomo's A_SetSpeed patch.
- fixed: Since the serializing code cannot distinguish between user variables of the same name coming from different actors in an inheritance chain, this kind of name duplication must be prohibited.
- fixed: When the SectorAction's TriggerAction method was renamed, the inherited one in the MusicChanger was overlooked. (Bit thanks to the C++ specs for allowing to override a non-virtual method with a virtual one without even showing a warning...)
Merge branch 'master' of https://github.com/rheit/zdoom into osx