tree-optimization/116010 - dr_may_alias regression

r15-491-gc290e6a0b7a9de fixed a latent issue with dr_analyze_innermost
and dr_may_alias where not properly analyzed DRs would yield an invalid
answer.  This caused some missed optimizations in case there is not
actually any evolution in the not analyzed base part.  The following
recovers this by only handling base parts which reference SSA vars
as index in the conservative way.

The gfortran.dg/vect/vect-8.f90 testcase is difficult to deal with,
so the following merely bumps the maximum number of expected vectorized loops
for both aarch64 and x86-64.

	PR tree-optimization/116010
	* tree-data-ref.cc (contains_ssa_ref_p_1): New function.
	(contains_ssa_ref_p): Likewise.
	(dr_may_alias_p): Avoid treating unanalyzed base parts without
	SSA reference conservatively.

	* gfortran.dg/vect/vect-8.f90: Adjust.