OGR input: add 2.5D support when USE_POINT_Z_M is defined
PostGIS input: add 2.5D support when USE_POINT_Z_M is defined

Consequently the PROCESSING option FORCE2D is assumed to be NO by
default when USE_POINT_Z_M is defined (related to #4803)
OGR output: fix export of line geometry as MultiPoint
GML output: export XYZ when USE_POINT_Z_M is defined and gml_geomtype is set to Point25D/LineString25D/etc.. (same syntax as 2.5D OGR output)
Autotest: build with WITH_POINT_Z_M=1
Update msautotest