Files opened without an explicit ACTION= specifier#
The Fortran standard says that if an OPEN statement is executed
without an explicit ACTION= specifier, the default value is
processor dependent.  GNU Fortran behaves as follows:
- Attempt to open the file with - ACTION='READWRITE'
- If that fails, try to open with - ACTION='READ'
- If that fails, try to open with - ACTION='WRITE'
- If that fails, generate an error