runtime: white space removal.
controlport: adding a 'toggle' interface for ControlPort.

This is very similar and accessed like a 'set' function only it does not take a parameter; it simply calls a function. Meant to toggle an action, like reseting the performance counters or locking/unlocking the flowgraph.
controlport: allows reset_perf_counters to be called over controlport; gr-perf-monitorx has button to call this.

Also changes the icon of the ControlPort tools to the new one.
cmake and build: fixes for cross-compiling to enable ControlPort with ICE.
digital: pfb_clock_sync throws when no taps are provided (instead of segfaulting).
Merge branch 'maint'
Merge branch 'cmake_oe_fixes'
Merge branch 'ctrlport_trigger'
Merge branch 'master' into next