PR bootstrap/84405
	* system.h (BROKEN_VALUE_INITIALIZATION): Define for GCC < 4.3.
	* vec.h (vec_default_construct): Use memset instead of placement new
	if BROKEN_VALUE_INITIALIZATION is defined.
	* hash-table.h (hash_table<Descriptor, Allocator>::empty_slow): Use
	memset instead of value initialization if BROKEN_VALUE_INITIALIZATION
	is defined.

From-SVN: r257726