controlport: added support for complex data types.

Vectors of complex are still passed as interleaved. Single values can be passed as GNURadio::complex. ControlPort can translate these in GNU Radio to gr_complex; Python programs need to convert themselves. gr-ctrl-monitor updated to handle this.

multiply_const_cc block updated to export get and set of k value through ControlPort.
Update revision to 3.7.0rc0
runtime: fixed checks on vmcircbuf file and mutex locking for creation and usage of vmcrcbuf classes.
Merge branch 'master' of git.gnuradio.org:gnuradio
core: made strncmp instead of strcmp in case of new lines.
Merge branch 'maint'
wxgui: Fixes to solve issues using GL sinks on OS X

plotter/plotter_base.py:

* Create explicit OpenGL context, check if window is shown before
realising context & only create PaintDC is paint triggered by WM
message (OS paint event)

* Added SetSizeHints to WX sink windows so sizing occurs correctly
wxgui: fix issue with flickering on Linux created by bea6d506
cmake: make install directory of GNU Radio cmakes files configurable
blocks: fix big-endian issue in wavefile blocks
blocks: fix param test in keep_me_in_n GRC wrapper
core: ensure message passing blocks marked done are handled
Merge branch 'fix-wxgui-gl' into maint
Merge branch 'maint'

Conflicts:
	gnuradio-core/src/lib/runtime/gr_tpb_thread_body.cc
core: fir_filter_with_buffer using consistent error margins in all QA tests.

Addresses issue #553.
Merge branch 'maint'
ctrlport: fixed an issue where we weren't using a standard C++ way to set complex values.
grc: revert ce52bd370 fixes problem with order
grc: allow multiple ports with varying nchan
grc: fix port names (index relative to port type not absolute)