Fixed|libdoom|Definitions: Don't apply glow to Plutonia's FIREBLU material

The IWAD version of this animation depicts a slimy rock surface
that should not appear to glow.

Issue #1849
Fixed|libdoomsday|DED: Parsing Flags with an implicit zero value

If no value is specified for a Flag then we should assume zero. This
fixes an XG regression where the value for ltc_none flag was being
registered with an uninitialized value.
Fixed|Renderer|LensFlares: Failed (viewPlayer - ddPlayers == displayPlayer) assertion

Todo: Needs further investigation.
Fixed|Resources: Handle the case of a zero-length lump between S(*)_START/_END

Some intrepid mod authors may insert a zero-length lump here, which
is then "replaced" with a high-resolution resource later.
libcommon: Cmd "stopinf" now always returns true

This prevents spurious alerts regarding attempts to stop scripts which
are not currently running. Older mods often call the stopinf command
without knowing if the script is running or not, "just to make sure".
Debug|libcommon|XG: Assert XL_DoFunction's parameters are valid
Merge branch 'master' into common-episode-definition