As reported internally by Frederik, gfortran currently passes 
LOCATION_COLUMN == 0 to the middle end. The reason for that is how 
parsing works – gfortran reads the input line by line.

For internal error diagnostic (fortran/error.c), the column location was 
corrected –  but not for locations passed to the middle end. Hence, the 
diagnostic there wasn't optimal.

Fixed by introducing a new function; now one only needs to make sure 
that no new code will re-introduce "lb->location" :-)

Build and regtested on x86-64-gnu-linux.
OK for the trunk?

Tobias