[vdr] Makefile variable names LCLBLD and PLGCFG

Hello,

Should probably have spoken earlier, but is there any particular reason for the ugly and hard to read Makefile variable names LCLBLD and PLGCFG? I suppose they're short for LOCALBUILD and PLUGINCONFIG, but why do they have to be short for anything, it's not like we're running out of space for their names anywhere, is it? Besides, I don't think LCLBLD describes what its effects are very well, INPLACE would sounds better to me.

The ship may already have sailed for plgcfg in vdr.pc as it's being used by many plugin Makefiles already, but I believe the attached patches should be safe for 2.0.0.