Added convolve method and RealFirFilter class.
Added "trimTails" option to convolve method.
Moved convolve methods to DspBuffer.
Restructered convolve a bit and added tests for the other classes.
Convolve now modifies "this" instead of creating a new object.
Added sum, diff, and running diff methods.
Added decimate method.
Added the interp method.  Doesn't work yet.
Fixed interp method
Got "trimTails" option of interp method working.
Changed scratchBuf so multiple objects can share one scratchBuf.
Cleaned up scratchBuf stuff.

Also renamed "convolve" to "conv".
Cleaned up lots of compile warnings.
Initial pass at resample method.
Got resample method working.
Added filter tests to ComplexDspBufferTest and RealDspBufferTest.
Added angle method to ComplexDspBuffer.
Created angle and magSq functions for std::complex.
Added doxygen comments to DspBuffer.
Added doxygen comments for functions.

Doxygen doesn't seem to include them in the documentation though.  I'll have to see what's up with that.