Reverted html markup for mathematical expressions in ST_Touches and ST_Crosses...

Reverted html markup for mathematical expressions in ST_Touches and ST_Crosses to a gif image.  It seems unicode markup does not work well for both IE and Firefox.  The next best thing to do is to get MathML markup working.

git-svn-id: http://svn.osgeo.org/postgis/trunk@2906 b70326c6-7e19-0410-871a-916f4a2858ee