Audio widget experimental

I made some changes to audio-widget code in a forked repo off of sdr-widget:
1. Make it possible to specify where the cross compiler and assembler would look for header files via the -I option in CFLAGS or ASFLAGS, defined in makefile.defs and passed to all the Release/*/subdir.mk files.
2. Added my own USB PID/VIDs to the list.
I would like to see these changes go into the main tree.