gengroup fails to generate output to a directory that does not previously exist. For example:
$ $MLE_ROOT/bin64/gengroup -l -d dxs win32:directx ../workprints/HelloWorld.dwp actorid.h groupid.h
reading Include
reading SetDef
reading HeaderFile
reading PropertyDef
reading PropertyDef
reading Stage
reading Set
reading Property
reading Property
reading Scene
reading Group
Unable to open dxs\actorid.h: 2
M:\Projects\MagicLantern\bin64\gengroup.exe : Unable to initialize Actor/Group output
In this case, the directory 'dxs' does not exist.
