AH (Ad Hoc) waveform format read support

AH v1 should be fine.
AH v2 tests need some real examples + ASCII equivalents to finish this PR - unfortunatly I couldn't find anything useable :/

Anyone got some AH v2 files? @jsaul, @jwassermann?
Maybe also raise a warning saying that AH 2.0 support is untested and they please send us a test file?