* dwarf2loc.c (dwarf_expr_frame_base): Constify.

	* dwarf2loc.c (dwarf_expr_frame_base): Constify.
	(dwarf_expr_frame_base_1): Likewise.
	(read_pieced_value): Update.
	(needs_frame_frame_base): Constify.
	(dwarf2_tracepoint_var_loc): Likewise.
	(dwarf2_tracepoint_var_access): Likewise.
	(locexpr_describe_location_piece): Likewise.
	(locexpr_describe_location_1): Likewise.
	* dwarf2expr.h (struct dwarf_expr_context) <get_frame_base>:
	Constify.
	(data): Now const.
	(struct dwarf_expr_piece) <v.literal.data>: Likewise.
	(dwarf_expr_eval, read_uleb128, read_sleb128)
	(dwarf2_read_address): Update.
	* dwarf2expr.c (dwarf_expr_eval): Constify.
	(read_uleb128): Likewise.
	(read_sleb128): Likewise.
	(dwarf2_read_address): Likewise.
	(require_composition): Likewise.
	(execute_stack_op): Likewise.
	* dwarf2-frame.h (struct dwarf2_frame_state_reg) <loc.exp>: Now a
	"const gdb_byte *".
	* dwarf2-frame.c (struct dwarf2_frame_state_reg_info) <cfa_exp>:
	Now const.
	(no_get_frame_base): Constify.
	(execute_stack_op): Likewise.
	(execute_cfa_program): Likewise.
	(read_encoded_value): Likewise.