vect: Reject uncounted loop vectorization where alias analysis may fail

vect: Reject uncounted loop vectorization where alias analysis may fail

Issues with alias list pruning for uncounted loops was found to cause
as-of-yet unresolved issues in the execution of SpecV6.  Disable this
while a reduced testcase is developed and a solution implemented.

Test derived from "omp_get_partition_place_nums" from libgomp "icv.c":

unsigned len = 8;

void
alias_fail (int n[8])
{
  unsigned int i;
  for (i = 0; i < len; i++)
    *n++ = i;
}

gcc/ChangeLog:

	* tree-vect-data-refs.cc (vect_prune_runtime_alias_test_list):
	Reject when !operand_equal_p for any data ref pair.