gdb/fortran: add support for 'SIZE' keyword

gdb/fortran: add support for 'SIZE' keyword

Add support for the 'SIZE' keyword to the Fortran expression parser.
This returns the number of elements either in an entire array (passing
a single argument to SIZE), or in a particular dimension of an
array (passing two arguments to SIZE).

At this point I have not added support for the optional third argument
to SIZE, which controls the exact integer type of the result.

gdb/ChangeLog:

	* f-exp.y (eval_op_f_array_size): Declare 1 and 2 argument forms
	of this function.
	(expr::fortran_array_size_1arg): New type.
	(expr::fortran_array_size_2arg): Likewise.
	* f-exp.y (exp): Handle FORTRAN_ARRAY_SIZE after parsing
	UNOP_OR_BINOP_INTRINSIC.
	(f77_keywords): Add "size" keyword.
	* f-lang.c (fortran_array_size): New function.
	(eval_op_f_array_size): New function, has a 1 arg and 2 arg form.
	* std-operator.def (FORTRAN_ARRAY_SIZE): New operator.

gdb/testsuite/ChangeLog:

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