Refactor|Map Renderer|Client: Consolidated drawing of generator debug visuals; cleanup
Refactor|Map Renderer|Client: Consolidated drawing of sound emitter debug visuals; cleanup
Fixed|World|Client: Attempt to free pointer without ZONEID following failed map load

The "objlink" blockmap allocates storage for global data from the
memory zone with the PU_MAP/MAPSTATIC purge level. Whenever the
current map changes we must clear this data explicitly as a zone
purge will leave internal pointers dangling.
Merge branch 'master' of github.com:skyjake/Doomsday-Engine