[Opensg-core] [OpenSG2, Patch] Buildsystem reworked

[Carsten N. <car...@gm...>]

	Hi,

the attached patch changes the build to not use variants (of
scons-addons) and moves almost all build logic into the top level
SConstruct (instead of the SConstruct, Source/Sconscript split). The
build.info files are now obsolete, however every directory to be
considered must contain a SConscript file that associates the files in
that directory with one of the libraries (similar to the common.mk files
of old).
I'd appreciate it if you could try this out and give me some feedback on
your experience (I might have accidentally killed your favorite feature
;) ).

	Thanks,
		Carsten