prussdrv: remove debug prints in release builds

This change adds a macro to optionally compile out the debug printfs
placed throughout the code. Debug builds have the prints. Release builds
do not.

Trailing whitespace was also removed in several places.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
prussdrv: return error when exec_program fails

Add error returns to a couple error checks in prussdrv_exec_program
that only printed error messages to the console.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Merge pull request #11 from fhunleth/debugprints

Remove debug prints in release builds and return error when fopen/fread fail