TC: int _close( int fh )

	- prototype in io.h

	- closes file fh where fh is file handle from _creat(), creat(),
	  creatnew(), creattemp(), dup(), dup2(), _open(), or
	  open().
	- use fdopen() to change file handle to file stream.
	- does not write a Ctrl-Z to a text file on closing
	- returns 0 if OK;  -1 & errno=EBADF
	- MS C uses _dos_close()

	- see	INT 21,3E