problem when using a geographic CRS after changing the central meridian

[lutra]

Tested with both shapefiles and postgis.

How to reproduce the problem:

*) download this shapefile of the world borders ​http://thematicmapping.org/downloads/TM_WORLD_BORDERS-0.3.zip

*) add it to your project

*) add a custom CRS with the following definition (for example) "+proj=moll +lon_0=Central Meridian +x_0=False Easting +y_0=False Northing"

*) in the project properties choose the just created CRS and activate OTFR

*) the layer shows correctly

*) now go to the CRS management and change the central meridian "+proj=moll +lon_0=90 +x_0=False Easting +y_0=False Northing"

*) in the project properties change again to wgs84 and back again to the custom CRS, now the shape looks weird.

*) if you zoom in enough the problem disappear

[homann]

This is a duplicate of #597. As you can see the American continent wraps around, which means the polygons should really by split.

Basically, you can't set up your projections such that geometries must be split.