Modify function ST_Buffer() to handle geographic coordinates correctly

[krandalf75]

[krandalf75]

Article about Geodesic Buffering: http://www.esri.com/news/arcuser/0111/geodesic.html

[krandalf75]

Postgis implements a simple approach: http://www.postgis.org/docs/ST_Buffer.html

For geography this is really a thin wrapper around the geometry implementation. 
It first determines the best SRID that fits the bounding box of the geography object 
(favoring UTM, Lambert Azimuthal Equal Area (LAEA) north/south pole, and falling 
back on mercator in worst case scenario) and then buffers in that planar spatial ref 
and retransforms back to WGS84 geography.

See the current implementation on the function geography_bestsrid() in file http://svn.osgeo.org/postgis/trunk/postgis/geography_measurement.c