actually only testcase added as the bug was fixed already.

modified:
  mysql-test/r/gis-precise.result
bug #857050 ST_WITHIN returns wrong result with MULTIPOINT and POLYGON
        test result updated.
  mysql-test/t/gis-precise.test
bug #857050 ST_WITHIN returns wrong result with MULTIPOINT and POLYGON
        test case added.
  sql/gcalc_tools.cc
        superfluous variable removed.