Problem: there was no standard syntax error when
         creating partitions with syntax error in
         the partitioning clause.

Solution: added "Syntax error: " to the error message


mysql-test/r/partition.result:
  Bug#29368: Incorrect error for syntax error when createing
             partition
  
  test result update
mysql-test/r/partition_error.result:
  Bug#29368: Incorrect error for syntax error when createing
             partition
  
  test result
mysql-test/t/partition_error.test:
  Bug#29368: Incorrect error for syntax error when createing
             partition
  
  test case
sql/share/errmsg.txt:
  Bug#29368: Incorrect error for syntax error when createing
             partition
  
  Modified error messages