uhd: enhanced version of usrp_spectrum_sense.py
Merge branch 'master' into next

Conflicts:
	gr-uhd/examples/python/usrp_spectrum_sense.py
runtime: fix for gr_enabled_realtime_scheduling
build: fixed GnuradioConfig files for OOTs to use.
docs: fixed warnings.
Merge branch 'master' into next

Conflicts:
	CMakeLists.txt
build: updated config cmake file for next changes.
runtime: id docstring clearer
Merge branch 'master' into next
build: removed some old autotools-related documentation.
Merge branch 'master' into next
runtime: fix for thread safety issue during simultaneous use of stream tags and performance counters
Merge branch 'maint'
Merge branch 'master' into next
runtime: forgot to go back to the 'old' style using gruel.
Merge branch 'maint'
Merge branch 'master' into next
cmake: updated GnuradioConfig.cmake file to look for headers installed in 3.6.
Merge branch 'master' into next

Conflicts and updated for 3.7 changes:
	cmake/Modules/GnuradioConfig.cmake
modtool: added comment to modtool's generated root CMakeLists.txt file to describe use of GnuradioConfig.cmake.