spgram: adding methods to accumulate power spectral density internally

  * added two new methos
  * names and interfaces not particularly intuitive
  * functional for now, but needs work
Merge branch 'master' into spgram-dev
autotest: removing redundant -u flag for usage/help
msresamp: fixing bug with allocating half-band resamplers

  * called malloc() on arbitrary resamp object
  * should have allocated for resamp2 object
  * probably not an issue considering resamp is larger than resamp2
msresamp: adding brief description to msresamp example to README
dotprod: fixing bug with dotprod_rrrf for SSE4
filter/firfilt: adding firfilt_crcf example
filter: adding descriptive comments to method prototypes
firfilt: clear() -> reset()
filter/firfilt: adding internal scaling factor

  * not particularly useful for floating point implementations
  * more useful for fixed-point implementations
  * fixed: use full range of bit resolution, scale at the end
  * fixed: will need some way to implement scaling with shifts
Merge branch 'master' of liquidsdr/liquid-dsp
dotprod: adding descriptive comments to method prototypes
build: removing antiquated/commented line to check for liquid-fpm
autocorr: adding descriptive comments to method prototypes
autocorr: clear() -> reset(), adding descriptive comments
iirfilt: adding descriptive comments to method prototypes
iirfiltsos: adding descriptive comments to method prototypes
iirfilt/iirfiltsos: clear() -> reset()
firpfb: adding descriptive comments to method prototypes
firpfb: clear() -> reset()