Fortran specific: Add logical XOR ops for compiler compliance

Add Fortran specific XOR ops for logical types to GDB, to provide
the same functionality as GFORT.

2013-10-01  Christoph Weinmann  <christoph.t.weinmann@intel.com>

gdb/
	* eval.c (evaluate_subexp_standard): Add case for
	BINOP_LOGICAL_XOR.
	* f-exp.y : Add rule for BINOP_LOGICAL_XOR, extend struct
	f77_keywords.
	* f-lang.c (f_op_print_tab): Add XOR opcode to print
	precedence struct.
	* parser-defs.h (precedence): Add XOR opcode to precedence
	struct.
	* std-operator.def : Add XOR opcode to opcode list.

gdb/testsuite/
	* logical_xor.f90 : Fortran program for logical OR and XOR
	printing.
	* logical_xor.exp : Test for printing Fortran logical OR
	and XOR operations.

Change-Id: Ic1a702e6dc080adbe206bb77f2064fea4bba7290