the SphericalMercator mixin register two transformations to/from EPSG:900913,
EPSG:4326. Thanks to Tim for the feedback and review. (Closes#1210)
This allows us to transform points to/from SphericalMercator
without proj4js support -- and if other projects need similar functionality,
they can write their own custom transformation functions rather than
modifying proj4js to support some custom projection.
git-svn-id: http://svn.openlayers.org/trunk/openlayers@5410 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf