[PR100843] store by mult pieces: punt on max_len < min_len

The testcase confuses the code that detects min and max len for the
memset, so max_len ends up less than min_len.  That shouldn't be
possible, but the testcase requires us to handle this case.

The store-by-mult-pieces algorithm actually relies on min and max
lengths, so if we find them to be inconsistent, the best we can do is
punting.


for  gcc/ChangeLog

	PR middle-end/100843
	* builtins.c (try_store_by_multiple_pieces): Fail if min_len
	is greater than max_len.

for  gcc/testsuite/ChangeLog

	PR middle-end/100843
	* gcc.dg/pr100843.c: New.