[libgfortran,commited] Add O_RDWR to open() call

[FX Coudert]

The second argument to open(), namely the flags with which the file is 
to be opened, is a bitwise-inclusive OR of flags. It should contain 
exactly one of O_RDWR, O_RDONLY, O_WRONLY 
(http://www.opengroup.org/onlinepubs/009695399/functions/open.html)

The open() call used to create scratch files in libgfortran didn't have 
any of those three flags, and gfortran wasn't able to use scratch files 
correctly on mingw32. A trivial patch, commited as obvious on 4.0 and 
mainline, fixes this. Commit messages:

http://gcc.gnu.org/ml/gcc-cvs/2005-08/msg00191.html
http://gcc.gnu.org/ml/gcc-cvs/2005-08/msg00192.html

FX