gdb/

gdb/
	Fix PR 10640.
	* dwarf2-frame.c (no_dwarf_call): New function.
	(execute_stack_op): Set CTX->DWARF_CALL.
	* dwarf2expr.c (execute_stack_op) <DW_OP_call2, DW_OP_call4>: New.
	* dwarf2expr.h (struct dwarf_expr_context) <dwarf_call>: New.
	(struct dwarf_expr_context) <get_subr>: Remove the #if0-ed field.
	* dwarf2loc.c (per_cu_dwarf_call, dwarf_expr_dwarf_call): New functions.
	(dwarf2_evaluate_loc_desc): Initialize CTX->DWARF_CALL.
	(needs_frame_dwarf_call): New function.
	(dwarf2_loc_desc_needs_frame): Initialize CTX->DWARF_CALL.
	* dwarf2read.c (follow_die_offset): Based on former follow_die_ref.
	Update the comment.  Move variables die, offset and error call to ...
	(follow_die_ref): ... a new function.
	(dwarf2_fetch_die_location_block): New function.
	* dwarf2loc.h (dwarf2_fetch_die_location_block): New prototype.

gdb/testsuite/
	Test PR 10640.
	* gdb.dwarf2/dw2-op-call.exp, gdb.dwarf2/dw2-op-call.S: New.