Convert dwarf_expr_context_funcs to methods

Convert dwarf_expr_context_funcs to methods

This patch converts the function pointers in dwarf_expr_context_funcs
into methods on dwarf_expr_context, and then updates the various
implementations and callers to follow.

NB this patch uses "override" (which caught a couple of renaming bugs
during development) -- but this is C++11, so this patch at least has
to wait for Pedro's patch that adds the OVERRIDE macro.

After this patch it would be possible to do one more, that makes
various members of dwarf_expr_context "protected"; but I haven't done
this.

2016-10-21  Tom Tromey  <tom@tromey.com>

	* dwarf2loc.c (struct dwarf_expr_context_funcs): Don't declare.
	(dwarf_expr_read_addr_from_reg, dwarf_expr_get_reg_value)
	(dwarf_expr_read_mem, dwarf_expr_frame_base): Rename; turn into
	methods.
	(get_frame_pc_for_per_cu_dwarf_call): New function.
	(dwarf_expr_frame_cfa, dwarf_expr_frame_pc)
	(dwarf_expr_tls_address): Rename; turn into methods.
	(per_cu_dwarf_call): Remove arguments.  Use
	get_frame_pc_for_per_cu_dwarf_call.
	(dwarf_evaluate_loc_desc): New class.
	(dwarf_expr_dwarf_call, dwarf_expr_context)
	(dwarf_expr_push_dwarf_reg_entry_value)
	(dwarf_expr_get_addr_index, dwarf_expr_get_obj_addr): Rename; turn
	into methods.
	(dwarf_expr_ctx_funcs): Remove.
	(dwarf2_evaluate_loc_desc_full): Update.
	(dwarf2_locexpr_baton_eval): Update.
	(symbol_needs_eval_context): New class.
	(symbol_needs_read_addr_from_reg, symbol_needs_get_reg_value)
	(symbol_needs_read_mem, symbol_needs_frame_base)
	(symbol_needs_frame_cfa, symbol_needs_tls_address)
	(symbol_needs_dwarf_call, needs_dwarf_reg_entry_value): Rename;
	turn into methods.
	(needs_get_addr_index, needs_get_obj_addr): Remove; turn into
	methods.
	(symbol_needs_ctx_funcs): Remove.
	(dwarf2_loc_desc_get_symbol_read_needs): Update.
	* dwarf2expr.h (struct dwarf_expr_context_funcs): Remove; turn
	contents into methods.
	(struct dwarf_expr_context) <baton, funcs>: Remove.
	<read_addr_from_reg, get_reg_value, read_mem, get_frame_base,
	get_frame_cfa, get_frame_pc, get_tls_address, dwarf_call,
	impl_get_base_type, push_dwarf_block_entry_value, get_addr_index,
	get_object_address>: Declare new methods.
	(ctx_no_get_frame_base, ctx_no_get_frame_cfa)
	(ctx_no_get_frame_pc, ctx_no_get_tls_address, ctx_no_dwarf_call)
	(ctx_no_get_base_type, ctx_no_push_dwarf_reg_entry_value)
	(ctx_no_get_addr_index): Don't declare.
	* dwarf2expr.c (get_base_type): Use impl_get_base_type.
	(execute_stack_op): Update.
	(ctx_no_get_frame_base, ctx_no_get_frame_cfa)
	(ctx_no_get_frame_pc, ctx_no_get_tls_address, ctx_no_dwarf_call)
	(ctx_no_get_base_type, ctx_no_push_dwarf_reg_entry_value)
	(ctx_no_get_addr_index): Remove; now methods on
	dwarf_expr_context.
	* dwarf2-frame.c (read_addr_from_reg): Take a frame_info, not a
	baton.
	(class dwarf_expr_executor): New class.
	(get_reg_value, read_mem): Rename, turn into methods.
	(execute_stack_op): Use dwarf_expr_executor.