Factor C flags out to proper locations
Factor C flags out to proper locations

Most of the C flags taken from the GT.M makefile and hard-coded
in CMAKE_C_FLAGS were already added in other places.  Default to
"Release" configuration so the flags are used when no configuration
is selected.

luisibanez/fis-gtm,luisibanez/fis-gtm,luisibanez/fis-gtm,luisibanez/fis-gtm