qtgui: apps: with new use of the Title, the titles provided here just take up extra screen real estate.
blocks: UDP source does not enforce IPv4 anny more
blocks: UDP sink does not enforce IPv4
qtgui: remove direct calls to aligned volk kernels; using dispatchers instead.

Addresses problem of using FFTW buffers on AVX machines (when FFTW is not built with AVX).

Addresses Issue #645.
Merge branch 'maint'