gdb/fortran: support ALLOCATED builtin

gdb/fortran: support ALLOCATED builtin

Add support for the ALLOCATED keyword to the Fortran expression
parser.

gdb/ChangeLog:

	* f-exp.y (f77_keywords): Add allocated.
	* f-lang.c (evaluate_subexp_f): Handle UNOP_FORTRAN_ALLOCATED.
	(operator_length_f): Likewise.
	(print_subexp_f): Likewise.
	(dump_subexp_body_f): Likewise.
	(operator_check_f): Likewise.
	* std-operator.def (UNOP_FORTRAN_ALLOCATED): New operator.

gdb/testsuite/ChangeLog:

	* gdb.fortran/allocated.exp: New file.
	* gdb.fortran/allocated.f90: New file.