Control input interpolator design (using Sympy)
New simple gain plugin (C source file)
Add manifest.ttl for the new Gain plugin
Optimized gain for constant gain input
Specific HEXD_LIBS directives & -lm for hexd-gain
PLUGIN_URI now got from plugin dirname
Add manifest.ttl for new hexd-lowpass plugin
Add C source file for the hexd-lowpass plugin
New hexd.h with "boilerplate function" macros
Cubic "control" interpolator structs & macros
Makefile on .c updates; Some code uniformization