Move Type_handler_geometry code from sql_type.h/cc to sql_type_geom.h/cc

We'll eventually move all GIS data types into a plugin. So the GIS related code should reside in separate files. Under terms of this task let's move the GIS code from sql_type.h and sql_type.cc to new files sql_type_geom.h and sql_type_geom.cc.

Note, under terms of a separate task, Field_geom later will also be moved from field.h and field.cc to separate files.