Add support of splitting parameter classes to ARCH, DEFS, LIB

in ARCH, there are all -m flags (will be expanded into ARCH_FLAGS in Makefile)
in DEFS, there are all -D flags (will be expanded into DEFS in Makefile)
in LIB, there are all -l flags (will be expanded into LIBNAME in Makefile)

If no MODE option specified, the generator behaves as in previous version.