[xml] XML_IO_EBADF with xmlDocDump

[Danny Holstein <dgholstein gmail com>]

I'm trying to use 

int xmlDocDump (FILE * f, xmlDocPtr cur)

and consistently receive a XML_IO_EBADF (bad file descriptor)  fault.  I'm using LibXML2 Version 2.7.8 on Windows 10.

BTW: I successfully fopen() with modes = "w", "wb" but receive XML_IO_EBADF.  With modes "w+"  and "w+b", I get XML_IO_FLUSH.  Adding "c" to the modes doesn't change anything, "x" causes the fopen() to fail with a "file exists" error.