qtgui: fixed problem with new volk avx multiply kernel.

Was calling _a version of kernel, but the window is a std::vector, which is not guaranteed to be 32-byte aligned.
tags: adds get_tags_in_window helper function for handling tags. Also updates some docs.
Merge branch 'maint'
cmake: updates (basically reverts) commit 3c44ba0687b08.

ICE 3.4.2 must be run with GCC 4.6 or less. Versions >= 4.7 will not work. All versions of GCC tested compile ICE 3.5.0/1. This check tests the version of GCC and if it is /NOT/ less than 4.6 (and therefore 4.7 or greater), then issue an error and disable ControlPort.
runtime: adds a gr.tag_utils.python_to_tag to convert formatted dicts/lists/tuples to tag_t objects.

blocks: adds documentation to vector_source block on how to use the python_to_tag to emit tags with the data stream.
Merge branch 'maint'
qtgui: timing is handled in the blocks; removing the qt timer.

This update dramatically reduces the X server overhead of the QT sinks.
Merge branch 'maint'
qtgui: adds ability to set the graphics style rendering of the qtgui sinks.

Set through gr-qtgui.conf prefs file. Documented in QT GUI section of manual.
qtgui: fixed call to _a version of volk kernels for waterfall plots.

(same fix tha was applied to freq_sinks in bf6d843ebde3a36).
Merge branch 'maint'

Conflicts:
	gr-qtgui/lib/waterfall_sink_c_impl.cc
	gr-qtgui/lib/waterfall_sink_f_impl.cc

Conflict due to white space issues.
grc: fix error message in console when using qtgui blocks
build: moving the location of the config.h file in the build tree so we can access it in sources as gnuradio/config.h.

Also uses the config.h to pull out if we've defined GR_PERFORMANCE_COUNTERS to handle the setup_pc_rpc function if perf counters are/are not compiled in.
cmake: Adds GR_CTRLPORT as a define in the root directory to populate config.h properly.
Merge branch 'maint'
blocks: allow subtract block to take a single input to invert the sign.
blocks: allows null source/sink to output/input multiple streams.

Updats xml files to allow this and to set bus port connection vector to group ports.
filter: adds a ccf version of the fft filter.

Taps are converted to complex still, so no computational savings here. Just for convinience of setting taps (mostly in c++).
filter: use fft_filter inside pfb_decimator.

Depending on the decimation rate and filter size, filtering with time domain or freq domain can be slower/faster and rotating using expj or fft can be slower/faster. This enables users to decide which features to use.
filters: fixing up some minor issues with the analysis/synthesis filterbanks.

Also adds bus ports capabilities to these filterbanks. Using the GRP properties box, the vector for the bus ports can be set up to group and redirect each channel as necessary.