USE_LOGGING not propagated to LOGGING preprocessor macro

[nncarlson]

If USE_LOGGING=ON this is not propagated to a -DLOGGING compile line definition, which always results in an empty nf_logging.F90 file. (The NAG compiler refuses to accept an empty file.) This commit addresses this by simply removing the #ifdef from nf_logging.F90; it seems to be unnecessary because both the cmake and autoconf configurations seem to be very careful about only including this source file when USE_LOGGING is ON.

[WardF]

Thanks for the contribution, it is very much appreciated! I'll review this after the automated checks complete and merge for the upcoming release!

[nncarlson]

My first time seeing Travis-CI in action -- pretty slick! (albeit a little slow)

[WardF]

It is, and I highly recommend it if at all possible. It also can run much faster, but we're using docker for our test matrices (details here if you're interested) and that slows the process down a bit as well.

[WardF]

Ok, reverting this change after a fashion; it turns out the previous logic was correct. USE_LOGGING is set if nc_set_log_level is found in the netCDF C library. If it's not, then logging is not available.

I'm adding a message to the configuration summary to make it more clear whether logging is available or not.