Remove union exp_element

This removes union exp_element functions that either create such
elements or walk them.  struct expression no longer holds
exp_elements.  A couple of language_defn methods are also removed, as
they are obsolete.

Note that this patch also removes the print_expression code.  The only
in-tree caller of this was from dump_prefix_expression, which is only
called when expression debugging is enabled.  Implementing this would
involve a fair amount of code, and it seems to me that prefix dumping
is preferable anyway, as it is unambiguous.  So, I have not
reimplemented this feature.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* value.h (evaluate_subexp_with_coercion): Don't declare.
	* parse.c (exp_descriptor_standard): Remove.
	(expr_builder::expr_builder, expr_builder::release): Update.
	(expression::expression): Remove size_t parameter.
	(expression::~expression): Simplify.
	(expression::resize): Remove.
	(write_exp_elt, write_exp_elt_opcode, write_exp_elt_sym)
	(write_exp_elt_msym, write_exp_elt_block, write_exp_elt_objfile)
	(write_exp_elt_longcst, write_exp_elt_floatcst)
	(write_exp_elt_type, write_exp_elt_intern, write_exp_string)
	(write_exp_string_vector, write_exp_bitstring): Remove.
	* p-lang.h (class pascal_language) <opcode_print_table,
	op_print_tab>: Remove.
	* p-lang.c (pascal_language::op_print_tab): Remove.
	* opencl-lang.c (class opencl_language) <opcode_print_table>:
	Remove.
	* objc-lang.c (objc_op_print_tab): Remove.
	(class objc_language) <opcode_print_table>: Remove.
	* m2-lang.h (class m2_language) <opcode_print_table,
	op_print_tab>: Remove.
	* m2-lang.c (m2_language::op_print_tab): Remove.
	* language.h (struct language_defn) <post_parser, expression_ops,
	opcode_print_table>: Remove.
	* language.c (language_defn::expression_ops)
	(auto_or_unknown_language::opcode_print_table): Remove.
	* go-lang.h (class go_language) <opcode_print_table,
	op_print_tab>: Remove.
	* go-lang.c (go_language::op_print_tab): Remove.
	* f-lang.h (class f_language) <opcode_print_table>: Remove
	<op_print_tab>: Remove.
	* f-lang.c (f_language::op_print_tab): Remove.
	* expression.h (union exp_element): Remove.
	(struct expression): Remove size_t parameter from constructor.
	<resize>: Remove.
	<first_opcode>: Update.
	<nelts, elts>: Remove.
	(EXP_ELEM_TO_BYTES, BYTES_TO_EXP_ELEM): Remove.
	(evaluate_subexp_standard, print_expression, op_string)
	(dump_raw_expression): Don't declare.
	* expprint.c (print_expression, print_subexp)
	(print_subexp_funcall, print_subexp_standard, op_string)
	(dump_raw_expression, dump_subexp, dump_subexp_body)
	(dump_subexp_body_funcall, dump_subexp_body_standard): Remove.
	(dump_prefix_expression): Update.
	* eval.c (evaluate_subexp): Remove.
	(evaluate_expression, evaluate_type): Update.
	(evaluate_subexpression_type): Remove.
	(fetch_subexp_value): Remove "pc" parameter.  Update.
	(extract_field_op, evaluate_struct_tuple, evaluate_funcall)
	(evaluate_subexp_standard, evaluate_subexp_for_address)
	(evaluate_subexp_with_coercion, evaluate_subexp_for_sizeof)
	(evaluate_subexp_for_cast): Remove.
	(parse_and_eval_type): Update.
	* dtrace-probe.c (dtrace_probe::compile_to_ax): Update.
	* d-lang.c (d_op_print_tab): Remove.
	(class d_language) <opcode_print_table>: Remove.
	* c-lang.h (c_op_print_tab): Don't declare.
	* c-lang.c (c_op_print_tab): Remove.
	(class c_language, class cplus_language, class asm_language, class
	minimal_language) <opcode_print_table>: Remove.
	* breakpoint.c (update_watchpoint, watchpoint_check)
	(watchpoint_exp_is_const, watch_command_1): Update.
	* ax-gdb.h (union exp_element): Don't declare.
	* ax-gdb.c (const_var_ref, const_expr, maybe_const_expr)
	(gen_repeat, gen_sizeof, gen_expr_for_cast, gen_expr)
	(gen_expr_binop_rest): Remove.
	(gen_trace_for_expr, gen_eval_for_expr, gen_printf): Update.
	* ada-lang.c (ada_op_print_tab): Remove.
	(class ada_language) <post_parser, opcode_print_table>: Remove.

gdb/opencl-lang.c

@@ -973,11 +973,6 @@ public:
 
   enum macro_expansion macro_expansion () const override
   { return macro_expansion_c; }
-
-  /* See language.h.  */
-
-  const struct op_print *opcode_print_table () const override
-  { return c_op_print_tab; }
 };
 
 /* Single instance of the OpenCL language class.  */