Decimate: Correct scaling

Scaling of a couple of real decimators relied on right shifts -- behavior is unpredictable in C99. Fix by doing proper power-of-two divide.
Console: Function to set background color.
Decimate: Make fir_64_decim_2_real_s16_s16 more generic.
LCD: Add red color constant.
TPMS: Add basic FSK demodulator and decoder.
TPMS: Rename ASK code/files.