Use grep found by ./configure (and have ./configure look for it)

git-svn-id: http://svn.osgeo.org/postgis/trunk@10942 b70326c6-7e19-0410-871a-916f4a2858ee
give anchor friendly ids for chapter and sections (so if we shuffle in future anchor doesn't change)

git-svn-id: http://svn.osgeo.org/postgis/trunk@10952 b70326c6-7e19-0410-871a-916f4a2858ee
Merge http://github.com/postgis/postgis into svn-trunk