cmake: update revision to 3.7.4git
docs: Updated Doxy files, added search bar
Simplify correlate_access_code_tag_bb and fix bug leading to false
trigger.
Move correlate_access_code_tag_bb to non-deprecated GRC category and
deprecate the older correlate_access_code_bb.
Simplify some more.
modtool: Updates to OOT docs, enables doxygen, removes some doxygen warnings
grc: fix some PyGTK backwards compatibilty issues
qtgui: Adding a Number sink with options to set autoscale, layout style, colors, averaging.
gr-qtgui: Use dummy void* return value for pywidget if !ENABLE_PYTHON

This has two benefits:
 - If ENABLE_PYTHON is disabled during build, the method will still be
   there and just return NULL

 - During build of external projects / apps that don't necessarely want
   to have python included in the build, the exposed vtable is the same
   as the one from GR (whether or not python was enabled during GR build)

Without this, using those block from outside without the exact same option
as during GR build would result in crash.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
gr-qtgui: Expose the qwidget() method in the public interface

When constructing an UI from C++ only, having access to the underlying
qwidget is very helpful.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
grc: tabbed PropsDialog
Merge branch 'qtgui_numsink'
grc: show dummy blocks when opening grc blocks
grc: special colors for missing blocks
qtgui: adding a 'config' tab to qtgui sinks to set display/line config options (style, width, colors, etc.)
grc: tabbed props: no more double entries
grc: tabbed probs: fix initial error box height
qtgui: fixed number display for qwt 5.2, 6.0, and 6.1.
Merge remote-tracking branch 'smunaut/qtgui_fixes'
qtgui: fixes number sink to handle Python/C++ exposure (see: 6a78af5919133 and d9dbb6b489deb)