"have_profiling"

1) Renamed have_community_features server system variable to
have_profiling.
2) Removed eable-community-features configure option and
ENABLE_COMMUNITY_FEATURES macro.
3) Removed COMMUNITY_SERVER macro and replaced its usage by 
ENABLED_PROFILING.

Only --enable-profiling is now needed to enable profiling.
It was the only existing "community feature", so there was
no need for both configure options.

Using --enable-community-features will give a warning message
since it no longer exists.