Minor fix to COFF .section change

[Mark E.]

There seems to be another problem in my opinion as a consequence of the 
current default.

.section .foo,"w"
.section .foo2,"d"

produces:

  3 .foo          00000000  00000000  00000000  00000000  2**2
                  ALLOC, LOAD, CODE
  4 .foo2         00000000  00000000  00000000  00000000  2**2
                  ALLOC, LOAD, DATA

The !BFD version handles 'w' and 'd' the same way, I think the BFD version 
should too. Thoughts?