gdb:

gdb:
	* value.h (value_non_lval): Declare.
	* value.c (value_non_lval): New function.
	* eval.c (evaluate_subexp_standard) <UNOP_POSTINCREMENT,
	UNOP_POSTDECREMENT>: Call value_non_lval to ensure to return a
	non-lvalue.

gdb/testsuite:
	* gdb.base/exprs.exp: Add tests for pre-/post- in-/decrement operators.