re PR libfortran/91030 (Poor performance of I/O -fconvert=big-endian)

2019-07-21  Thomas König  <tkoenig@gcc.gnu.org>

	PR libfortran/91030
	* gfortran.texi (GFORTRAN_FORMATTED_BUFFER_SIZE): Document
	(GFORTRAN_UNFORMATTED_BUFFER_SIZE): Likewise.

2019-07-21  Thomas König  <tkoenig@gcc.gnu.org>

	PR libfortran/91030
	* io/unix.c (BUFFER_SIZE): Delete.
	(BUFFER_FORMATTED_SIZE_DEFAULT): New variable.
	(BUFFER_UNFORMATTED_SIZE_DEFAULT): New variable.
	(unix_stream): Add buffer_size.
	(buf_read): Use s->buffer_size instead of BUFFER_SIZE.
	(buf_write): Likewise.
	(buf_init): Add argument unformatted.  Handle block sizes
	for unformatted vs. formatted, using defaults if provided.
	(fd_to_stream): Add argument unformatted in call to buf_init.
	* libgfortran.h (options_t): Add buffer_size_formatted and
	buffer_size_unformatted.
	* runtime/environ.c (variable_table): Add
	GFORTRAN_UNFORMATTED_BUFFER_SIZE and
	GFORTRAN_FORMATTED_BUFFER_SIZE.

From-SVN: r273643