tree-optimization/120156 - ICE in ptr_derefs_may_alias_p

tree-optimization/120156 - ICE in ptr_derefs_may_alias_p

This picks the ptr_derefs_may_alias_p fix from the PR99954 fix
which said:  This makes us run into a latent issue in
ptr_deref_may_alias_decl_p when the pointer is something like &MEM[0].a
in which case we fail to handle non-SSA name pointers.  Add code
similar to what we have in ptr_derefs_may_alias_p.

	PR tree-optimization/120156
	* tree-ssa-alias.cc (ptr_deref_may_alias_decl_p): Verify
	the pointer is an SSA name.

(cherry picked from commit c290e6a0b7a9de5692963affc6627a4af7dc2411)