Collections were treated mistakenly, so the counter for the final UNION operation
        received the wrong value.
        As a fix we implement Item_func_buffer::Transporter::start_collection() method,
        where we set the proper operation and the operand counter.
        start_poly() and start_line() were also modified to function correctly for the 
        polygon as a part of a collection.

per-file comments:
  mysql-test/r/gis-precise.result
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        test result updated.

  mysql-test/t/gis-precise.test
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        test case added.

  sql/item_geofunc.cc
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        start_collection() implemented.

  sql/item_geofunc.h
bug #801199 Infinite recursion in Gcalc_function::count_internal with ST_BUFFER over MULTIPOINT
        Item_func_buffer::Transporter::start_collection() defined.