Fortran: Suppress bogus used uninitialized warnings [PR108889].

2024-07-18  Paul Thomas  <pault@gcc.gnu.org>

gcc/fortran
	PR fortran/108889
	* gfortran.h: Add bit field 'allocated_in_scope' to gfc_symbol.
	* trans-array.cc (gfc_array_allocate): Set 'allocated_in_scope'
	after allocation if not a component reference.
	(gfc_alloc_allocatable_for_assignment): If 'allocated_in_scope'
	not set, not a component ref and not allocated, set the array
	bounds and offset to give zero length in all dimensions. Then
	set allocated_in_scope.

gcc/testsuite/
	PR fortran/108889
	* gfortran.dg/pr108889.f90: New test.