Renew the COPYING gpl-2.0 with last version from gnu.org

git-svn-id: http://svn.osgeo.org/postgis/trunk@11519 b70326c6-7e19-0410-871a-916f4a2858ee
Fix spelling errors in st_makevalid documentation

Fixes a couple of spelling errors, and use the full word 'without' instead of the contraction 'w/out'.

git-svn-id: http://svn.osgeo.org/postgis/trunk@11521 b70326c6-7e19-0410-871a-916f4a2858ee