tree-assume: Fix UB in assume_query [PR118605]

The assume_query constructor does
assume_query::assume_query (function *f, bitmap p) : m_parm_list (p),
                                                     m_func (f)
where m_parm_list is bitmap &.  This is compile time UB, because
as soon as the constructor returns, m_parm_list reference is still
bound to the parameter of the constructor which is no longer in scope.

Now, one possible fix would be change the ctor argument to be bitmap &,
but that doesn't really work because in the only user of that class
we have
      auto_bitmap decls;
...
      assume_query query (fun, decls);
and auto_bitmap just has
  operator bitmap () { return &m_bits; }
Could be perhaps const bitmap &, but why?  bitmap is a pointer:
typedef class bitmap_head *bitmap;
and the EXECUTE_IF_SET_IN_BITMAP macros don't really change that point,
they just inspect what is inside of that bitmap_head the pointer points
to.

So, the simplest I think is avoid references (which cause even worse
code as it has to be dereferenced twice rather than once).

2025-01-23  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/118605
	* tree-assume.cc (assume_query::m_parm_list): Change type
	from bitmap & to bitmap.