Merge pull request #1 from pthedinger/master

Some cleanup and adding xpd.xml.
Reduce memory usage of analyzer.

   This commit changes the way buffering occurs in the analyzer.
   It constructs the windowed signal directly from the partial
   half buffers passed to it from the i2s_tap. This saves memory
   by not having to store a full buffer in each analyzer.
Add digital input ramp checking