Split rt_core/rt_api.c and rt_pg/rt_pg.c into smaller files.

git-svn-id: http://svn.osgeo.org/postgis/trunk@11719 b70326c6-7e19-0410-871a-916f4a2858ee
Fixes to make sure PostgreSQL version > 9.2 compile without warnings

git-svn-id: http://svn.osgeo.org/postgis/trunk@11720 b70326c6-7e19-0410-871a-916f4a2858ee