[Bug fortran/52668] New: Incorrect warning emitted by gfortran 4.7.0

["arnaud02 at users dot sourceforge.net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52668

             Bug #: 52668
           Summary: Incorrect warning emitted by gfortran 4.7.0
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: arnaud02@users.sourceforge.net


>cat qq.f
      module mm
      integer :: a, b
      common /mm1/ a, b
      end module mm
      program pp
      call aa()
      end program pp
      subroutine aa()
      use mm, only: a
      a = 1
      end subroutine aa
>/usr/local/gcc/gfortran470 -Wall qq.f
qq.f:9.9:

      use mm, only: a
         1
Warning: Unused module variable 'b' which has been explicitly imported at (1)
>/usr/local/gcc/gfortran470 --version | head -2
GNU Fortran (GCC) 4.7.0
Copyright (C) 2012 Free Software Foundation, Inc.

The warning is incorrect: in pp, b is *not* imported explicitly from mm. 
This is a regression with respect to gfortran 4.6.x.