coverity 1207185: vocoder: unitialized summed squared error
cmake: fix to make FindPortaudio compatible with CMake 2.6.
cmake: fix component force on to work as expected
gr-digital: remove redundant source file
build: adding fstream include files for pedantic compilers.
qtgui: bringing in line with required Qt 4.4.

setGraphicsSystem was introduced in 4.5; doing a version check before its use.
Merge branch 'maint' of git.gnuradio.org:gnuradio into maint