digital: fixes for SNR ests.

set_history: you keep using that word. I do not think it means what you think it means.
Merge branch 'maint'
docs: adds protection from generated files of components not configured.

Also removes a couple warnings in generating docs.
video-sdl: fix typo in .pc file
Merge branch 'maint'
digital: OFDM frame equalizer now as an option to work w/o len tag
digital: fix some issues w/ header parser/gen; QA, wrong OFDM symbol number calculation, bug that always returns PMT_NIL
volk: fix CentOS build failure with extra lib64 in path

Use updated GrBoost.cmake from main build
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
Merge branch 'maint'
uhd: added a usrp PC sync option
uhd: added getters for bandwidth setting and range
filter: added fractional_resampler as a renamed fractional_interpolator.

GRC block tree only references this new block and not the interpolator any longer.
blocks: fix file meta data source to handle repeat of files.
Merge branch 'maint'
runtime: changed remove_item_tag to only mark tags as deleted
Merge remote-tracking branch 'jblum/uhd_work'
blocks: fixed header documentation in repack_bits_bb
digital: Merge OFDM changes