Minor BS cleanup
Better approach to configuring multiple packages: omalloc/resources/factory

add: precious configure variables {OMALLOC/RESOURCES/FACTORY}_{LIBS/INCLUDES}
fix: also related minor fixes

NOTE: main changes are in m4/options.m4 and factory/configure.ac (which was the motivator for the whole thing)

NOTE2: the cleanup of "-I${top_srcdir}/.." and "-I${top_srcdir}/../factory/include" (and similar for builddir) in favor of {OMALLOC/RESOURCES/FACTORY}_INCLUDES
Minor BS cleanup: no need in -I${srcdir} and -I${builddir} in CPPFLAGS