- prod/atusb: added clock frequency test
- prod/doc/setup.hmac: added GSL (libgsl) build dependency
- prod/doc/setup.hmac: recommend use of NTP on the PC
- prod/doc/test.hmac: added atusb to the clock frequency section
- test.hmac: added more details on physical test setup
- setup.hmac: described SPECTRUM_MARGIN parameter
- setup.hmac: described process for generating the reference spectrum