c++: remove TREE_STATIC from constexpr heap vars [PR119162]

c++: remove TREE_STATIC from constexpr heap vars [PR119162]

While working on PR119162 it occurred to me that it would be simpler to
detect the problem of a value referring to a heap allocation if we stopped
setting TREE_STATIC on them so they naturally are not considered to have a
constant address.  With that change we no longer need to specifically avoid
caching a value that refers to a deleted pointer.

But with this change maybe_nonzero_address is not sure whether the variable
could have address zero.  I don't understand why it returns 1 only for
variables in the current function, rather than all non-symtab decls; an auto
variable from some other function also won't have address zero.  Maybe this
made more sense when it was in tree_single_nonzero_warnv_p before r7-5868?

But assuming there is some reason for the current behavior, this patch only
changes the handling of non-symtab decls when folding_cxx_constexpr.

	PR c++/119162

gcc/cp/ChangeLog:

	* constexpr.cc (find_deleted_heap_var): Remove.
	(cxx_eval_call_expression): Don't call it.  Don't set TREE_STATIC on
	heap vars.
	(cxx_eval_outermost_constant_expr): Don't mess with varpool.

gcc/ChangeLog:

	* fold-const.cc (maybe_nonzero_address): Return 1 for non-symtab
	vars if folding_cxx_constexpr.