One issue I found while I was trying to resolve bug 1190346 is that 'postgresql-devel' requires 'postgresql' package (which happens to be multilib unclean at this moment). I haven't found the reason for this requirement, one might be that that '/usr/bin/pg_config' is packaged in 'postgresql'. But because '*-devel' always requires '*-libs', we could probably put 'pg_config' into 'postgresql-libs'. Removing this binary from 'postgresql' would not hurt because 'postgresql' requires 'postgresql-libs'.
After discussion with Honza, we decided to move the 'pg_config' from postgresql to postgresql-devel (not into postgresql-libs). This is to minimize postgreqsl-libs payload which is definitely desired. http://pkgs.fedoraproject.org/cgit/postgresql.git/commit/?id=4034635788132a1590