gdb/fortran: Introduce fortran-operator.def file

gdb/fortran: Introduce fortran-operator.def file

Future commits will add more Fortran specific expression operators.

In preparation for these new operators, this commit adds a new
fortran-operator.def file similar to how GDB already has
ada-operator.def.

I've moved UNOP_KIND the Fortran specific operator I introduced in
commit 4d00f5d8f6c4 into this file, and renamed it to make it clearer
that the operator is Fortran specific.  I've then updated the Fortran
exp_descriptor table (exp_descriptor_f) to use entirely Fortran
specific functions that now handle UNOP_FORTRAN_KIND (the new name for
UNOP_KIND).

There should be no visible changes for standard users after this
commit, though for developers, the output when 'set debug expression
1' is now better, before:

  (gdb) p kind (l1)
  Dump of expression @ 0x2ccc7a0, before conversion to prefix form:
  	Language fortran, 5 elements, 16 bytes each.
  	Index                Opcode         Hex Value  String Value
  	    0          OP_VAR_VALUE  42  *...............
  	    1               OP_NULL  47730176  .N..............
  	    2          BINOP_INTDIV  47729184   J..............
  	    3          OP_VAR_VALUE  42  *...............
  	    4             UNOP_KIND  78  N...............
  Dump of expression @ 0x2ccc7a0, after conversion to prefix form:
  Expression: `Invalid expression
  (gdb)

and after:

  (gdb) p kind (l1)
  Dump of expression @ 0x294d0b0, before conversion to prefix form:
  	Language fortran, 5 elements, 16 bytes each.
  	Index                Opcode         Hex Value  String Value
  	    0          OP_VAR_VALUE  40  (...............
  	    1   unknown opcode: 224  44088544  ................
  	    2   unknown opcode: 208  44087504  ................
  	    3          OP_VAR_VALUE  40  (...............
  	    4     UNOP_FORTRAN_KIND  119  w...............
  Dump of expression @ 0x294d0b0, after conversion to prefix form:
  Expression: `KIND(test::l1)'
  	Language fortran, 5 elements, 16 bytes each.

  	    0  UNOP_FORTRAN_KIND
  	    1    OP_VAR_VALUE          Block @0x2a0bce0, symbol @0x2a0b8d0 (l1)
  $1 = 1
  (gdb)

gdb/ChangeLog:

	* gdb/expprint.c (dump_subexp_body_standard): Remove use of
	UNOP_KIND.
	* gdb/expression.h (exp_opcode): Include 'fortran-operator.def'.
	* gdb/f-exp.y (exp): Rename UNOP_KIND to UNOP_FORTRAN_KIND.
	* gdb/f-lang.c (evaluate_subexp_f): Likewise.
	(operator_length_f): New fuction.
	(print_subexp_f): New function.
	(op_name_f): New function.
	(dump_subexp_body_f): New function.
	(operator_check_f): New function.
	(exp_descriptor_f): Replace standard expression handling functions
	with new functions.
	* gdb/fortran-operator.def: New file.
	* gdb/parse.c (operator_length_standard): Remove use of UNOP_KIND.
	* gdb/std-operator.def: Remove UNOP_KIND.