Problem: Some of the gis source files take long time to compile,
and require lots of memory.

Solution:
Remove template argument CoordinateElementType from BG_models.
It is always double anyways.

Move templatized code out of item_geofunc_internal.h
add explicit template instantions.

(cherry picked from commit 32f1278485bf0791ae1bec7c287109e93222c9a0)

Conflicts:
	libmysqld/CMakeLists.txt
	sql/CMakeLists.txt
	sql/item_geofunc_internal.h
	sql/item_geofunc_setops.cc
	sql/spatial.cc
	sql/spatial.h