channels: adding GRC tone example
channels: fix for phase imbalance/alias in the specular component for Rician channels, switch phase accumulator to double precision, exporting step size to grcp
core: adding variance calcs to perf. counters.

Using running mean/variance algorithm from Knuth's Art of Computer Programming.
Merge branch 'master' into next

Conflicts:
	gnuradio-core/src/lib/runtime/gr_block.cc
	gnuradio-core/src/lib/runtime/gr_block.h
	gnuradio-core/src/lib/runtime/gr_block_detail.h
core: adding variance perf. counters to ctrlport.
core: adding new var perf. counters to swig interface.
Merge branch 'master' into next
Merge remote-tracking branch 'osh/next' into next