qtgui: fixes some bugs between qwt 5 and 6, some reorg.
Merge branch 'maint'
blocks: interleaved_char_to_complex grc xml fix
digital: updated narrowband examples with --lo-offset and --clock-source options
digital: fixed ofdm benchmark_tx. flowgraph was closing down before tx queue was empty
fft: fix XML import for logpwrfft block
cmake: force detection to Python 2.x only
runtime: fix hier_block2 disconnect_all()
Merge branch 'maint'