Keep orthographic projections consistent

[pkturner]

PROJ is changing the way it handles '+proj=ortho' in spec strings, as of version 7.2. Previously, that projection performed a spheroidal calculation, even with the WGS84 datum. With the change, PROJ uses the precise ellipsoidal shape when projecting.

I encountered and reported this in #2016, because I build Mapper on Linux where PROJ has been at version 7.2 for several months. The new PROJ alters the geographic coordinates of map objects, changing their alignment to georeferenced templates.

This PR includes a regression test of a GPX track template that fails with the latest PROJ due to the track becoming misaligned with the map. It also addresses the problem by inserting '+f=0' into every spec string that uses '+proj=ortho'.

The drawback to this way of keeping Mapper consistent is that it eliminates the possibility of using an ellipsoidal orthographic projection with Mapper, for the time being. The ellipsoidal version is superior, but probably does not matter for orienteering because the spheroidal projection distorts the scale by less than 1%. It looks to me that if this PR is accepted, then to regain support for ellipsoidal orthographic projections would require a new version of the XML file format, and a bigger code change than this one.