#449 add coloring in messages

[Simon Sobisch]

Following GCC:

-fdiagnostics-color[=WHEN]
-fno-diagnostics-color

using COBC_COLORS, with a fallback to GCC_COLORS (see link above) for configuration and if both are not set falling back to NO_COLORS for disabling before checking the "installation default", which is to be set via configure's --with-diagnostics-color=choice (to be copied into GnuCOBOL's configure script).

Note: for versions not implementing this, it is possible to use https://github.com/zaufi/pluggable-output-processor to get a reasonable highlighting.