gr: added GR_TEST_ENVIRONS to GrTest
blocks: fix missing dynamic tag implementation
Removing gruel from QA python paths.
channels: new frequency selective fading block
Merge remote-tracking branch 'osh/master'
Merge remote-tracking branch 'jblum/gr_test_extra_environs'
channels: selective fading model cleanup
runtime: fix for timer issue that was causing qtgui components to not plot
Merge remote-tracking branch 'osh/master'
Merge branch 'master' of github.com:gnuradio/gnuradio into runtime_pimpl
blocks: plateau_detector_fb is now a gr_block and forecasts

The detector actually could return 0 with insufficient input.
The forecast always requires at least 2*d_max_len.
However, forecast could be conditionalized to only
require this based on the last threshold detected.