blocks: Added multiply_matrix_ff

This block maps inputs to outputs by matrix multiplication.
Also includes QA.
blocks: Added multiply_matrix_cc
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
Merge branch 'maint'
cmake: make build type check insensitive to case
Merge remote-tracking branch 'martin/blocks/mult_matrix'