ST_AsGML for curve types

[mhugent]

Dear PostGIS team

Find attached a patch adding GML output for the curve types (circularstring, compoundcurve, curvepolygon, multicurve, multisurface). Cunit and sql tests are provided as well. As it is my second PostGIS contribution (after 7 years break), please review carefully.

Thanks, Marco

[pramsey]

Looks pretty good to me, thanks for including tests, etc. I'll have to see if the team is OK w/ a 2.1 add, it's new functionality, though not a new function signature, so perhaps could be added to 2.1.

[robe]

I think the code change is too big to risk going into a micro. Besides we don't release new functionaltiy in a micro because its too hard to explain to people who rely on new functionality — use 2.1.2 or higher (much easier to say use 2.2)

[pramsey]

Trunk at r12227