gdb/

gdb/
	* dwarf2expr.c (ctx_no_read_reg): New function.
	* dwarf2expr.h (ctx_no_read_reg): New declaration.
	* dwarf2read.c (read_2_signed_bytes, read_4_signed_bytes): Remove.
	(decode_locdesc_read_mem, decode_locdesc_ctx_funcs): New.
	(decode_locdesc): Replace by a caller of dwarf_expr_eval.

gdb/testsuite/
	* gdb.dwarf2/dw2-simple-locdesc.S: New file.
	* gdb.dwarf2/dw2-simple-locdesc.exp: New file.
	* gdb.dwarf2/dw2-stack-boundary.exp (check partial symtab errors):
	Change the expected string.