Add vendor-specific extension source files

src/Makefile

src/cntlr.h

src/cntlr_cmdu.c

src/cntlr_cmdu.h

src/cntlr_commands_impl.c

src/cntlr_extension.c

src/cntlr_extension.h

src/cntlr_map.c

src/cntlr_tlv.c

src/cntlr_tlv.h

src/config.c