[patch, testsuite] Committed test for PR 20520

[Thomas Koenig]

Hi,

I just committed the test case below so the bug can be closed.

The error message is less than ideal, but at least it is something.
Maybe I'll file a separate PR about translating error messages about
artificial variables to user's variables.

Regards

        Thomas

2018-10-31  Thomas Koenig  <tkoe...@gcc.gnu.org>

        PR fortran/20520
        * gfortran.dg/allocatable_uninitialized_1.f90: New test.

! { dg-do compile }
! { dg-options "-O -Wall" }
program main
  real,allocatable:: a(:),b(:)

   a(1)=2*b(1) ! { dg-warning "uninitialized" }

end