Checks for thd->killed state added to the long loops in geometry calculations.

per-file comments:
  sql/gcalc_slicescan.cc
Fix for bug #809849 spatial operations must be KILL-able.
        checks for TERMINATED_STATE added.
  sql/gcalc_slicescan.h
Fix for bug #809849 spatial operations must be KILL-able.
        defines added to include checks for termination in the
        library.
  sql/gcalc_tools.cc
Fix for bug #809849 spatial operations must be KILL-able.
        checks for TERMINATED_STATE added.
  sql/gcalc_tools.h
Fix for bug #809849 spatial operations must be KILL-able.
        TERMINATED_STATE pointers added.
  sql/item_geofunc.cc
Fix for bug #809849 spatial operations must be KILL-able.
  sql/item_geofunc.h
Fix for bug #809849 spatial operations must be KILL-able.