[patch, fortran, 4.9] Dependency and string length calculation improvements

[Dominique Dhumieres]

Thomas,

Your test gfortran.dg/dependency_40.f90 does not have depedencies and 
does not create a temporary (assuming that "-Warray-temporaries" does
not miss any) with/without your patch and with gcc4.6, 4.7, and 4.8.
4.5 gives a warning. I have tried a few variants attempting to create
a temporary without the patch and none with it, but did not succeeded
so far.

Cheers,

Dominique