_PyFile_FromFdUnicode.patch: create _PyFile_FromFdUnicode() function. It will be used in import.c to open a file using an unicode filename.

For _PyFile_FromFd(), I kept the previous behaviour: clear the exception on PyUnicode_DecodeFSDefault() error.

For fileobject.h: I used the same style than unicodeobject.h, one argument per line with their name. I prefer to write the argument name because the header can be used as a quick documentation.

As _PyFile_FromFd(), name is optional (can be NULL) for _PyFile_FromFdUnicode().