blocks: convert asserts to throwing runtime errors in keep_m_in_n ctor.
blocks: fixed up keem_m_in_n to handle relative rate and correct number of items in calls to work.

Original patch from Zhe Feng on mailing list.
build_guide: Make explicit we only support Qt4
filter: Fixes setting sample delay declaration for the PFB channelizer and in GRC.

Addresses issue #695.
filter: Fixes setting sample delay declaration for PFB synthesizer in GRC.

Addresses issue #695.
runtime: fix installation location of the gr_log_default.conf log configuration file.

Addresses issue #720.
cmake: Additional search path for QWT include files.

This is specific to QWT5. In 3.8, we will likely move to QWT6.

Addresses Issue #735.
audio: Fixes string format bug in ALSA error messages.

Addresses issue #736.
grc: yet another py26 incompatibility
grc: fix search entry box for old PyGTK versions
grc: update all flowgraphs when hiding port labels
grc: no icon in search entry box for old PyGTK versions
grc: fix lagging drag and drop
grc: fix missing xterm (Bug #725)
blocks: fixed relative rate in keep_m_in_n. It's m-in-n, not n-in-m.
grc: fix lagging drag and drop, round two
Merge remote-tracking branch 'gnuradio-wg-grc/maint_grcwg' into maint
blocks: benchmark scripts using wrong includes.
Removing use of 'and', 'or', and 'not' for &&, ||, and !.
fec: removed ber_tools; unnecessary and not exported. Replaced compber with call to VOLK's popcount.

Added QA for ber_bf block and provided documentation for it.