PR libfortran/20788
	Missing entry from previous commit:
	* io/unix.c (fd_to_stream): Add an avoid_mmap argument indicating
	we don't we to mmap this stream. Use fd_open instead of mmap_open
	in that case.
	(open_external): Call fd_to_stream with avoid_mmap = 0.
	(input_stream): Call fd_to_stream with avoid_mmap = 1.
	(output_stream): Likewise.
	(error_stream): Likewise.

	Really committing:
	* io/read.c (read_f): Accept 'e', 'E', 'd' and 'D' as first
	non-blank characters of a real number.

From-SVN: r99508