re PR tree-optimization/49768 (C99 style union initializations does not work as expected with optimizations)

	PR tree-optimization/49768
	* gimple-fold.c (fold_nonarray_ctor_reference): Return NULL
	if offset is smaller than bitoffset, but offset+size is bigger
	than bitoffset.

	* gcc.c-torture/execute/pr49768.c: New test.

From-SVN: r176437