guile: Add support for Guile 2.2.

guile: Add support for Guile 2.2.

This primarily updates code that uses the I/O port API of Guile.

gdb/ChangeLog
2020-06-28  Ludovic Courtès  <ludo@gnu.org>
            Doug Evans  <dje@google.com>

	PR gdb/21104
	* guile/scm-ports.c (USING_GUILE_BEFORE_2_2): New macro.
	(ioscm_memory_port)[read_buf_size, write_buf_size]: Wrap in #if
	USING_GUILE_BEFORE_2_2.
	(stdio_port_desc, memory_port_desc) [!USING_GUILE_BEFORE_2_2]:
	Change type to 'scm_t_port_type *'.
	(natural_buffer_size) [!USING_GUILE_BEFORE_2_2]: New variable.
	(ioscm_open_port) [USING_GUILE_BEFORE_2_2]: Add 'stream'
	parameter and honor it.  Update callers.
	(ioscm_open_port) [!USING_GUILE_BEFORE_2_2]: New function.
	(ioscm_read_from_port, ioscm_write) [!USING_GUILE_BEFORE_2_2]: New
	functions.
	(ioscm_fill_input, ioscm_input_waiting, ioscm_flush): Wrap in #if
	USING_GUILE_BEFORE_2_2.
	(ioscm_init_gdb_stdio_port) [!USING_GUILE_BEFORE_2_2]: Use
	'ioscm_read_from_port'.  Call 'scm_set_port_read_wait_fd'.
	(ioscm_init_stdio_buffers) [!USING_GUILE_BEFORE_2_2]: New function.
	(gdbscm_stdio_port_p) [!USING_GUILE_BEFORE_2_2]: Use 'SCM_PORTP'
	and 'SCM_PORT_TYPE'.
	(gdbscm_memory_port_end_input, gdbscm_memory_port_seek)
	(ioscm_reinit_memory_port): Wrap in #if USING_GUILE_BEFORE_2_2.
	(gdbscm_memory_port_read, gdbscm_memory_port_write)
	(gdbscm_memory_port_seek, gdbscm_memory_port_close)
	[!USING_GUILE_BEFORE_2_2]: New functions.
	(gdbscm_memory_port_print): Remove use of 'SCM_PTOB_NAME'.
	(ioscm_init_memory_port_type) [!USING_GUILE_BEFORE_2_2]: Use
	'gdbscm_memory_port_read'.
	Wrap 'scm_set_port_end_input', 'scm_set_port_flush', and
	'scm_set_port_free' calls in #if USING_GUILE_BEFORE_2_2.
	(gdbscm_get_natural_buffer_sizes) [!USING_GUILE_BEFORE_2_2]: New
	function.
	(ioscm_init_memory_port): Remove.
	(ioscm_init_memory_port_stream): New function
	(ioscm_init_memory_port_buffers) [USING_GUILE_BEFORE_2_2]: New
	function.
	(gdbscm_memory_port_read_buffer_size) [!USING_GUILE_BEFORE_2_2]:
	Return scm_from_uint (0).
	(gdbscm_set_memory_port_read_buffer_size_x)
	[!USING_GUILE_BEFORE_2_2]: Call 'scm_setvbuf'.
	(gdbscm_memory_port_write_buffer_size) [!USING_GUILE_BEFORE_2_2]:
	Return scm_from_uint (0).
	(gdbscm_set_memory_port_write_buffer_size_x)
	[!USING_GUILE_BEFORE_2_2]: Call 'scm_setvbuf'.
	* configure.ac (try_guile_versions): Add "guile-2.2".
	* configure: Regenerate.
	* NEWS: Add entry.

gdb/testsuite/ChangeLog
2020-06-28  Ludovic Courtès  <ludo@gnu.org>

	* gdb.guile/scm-error.exp ("source $remote_guile_file_1"): Relax
	error regexp to match on Guile 2.2.

gdb/doc/ChangeLog
2020-06-28  Ludovic Courtès  <ludo@gnu.org>

	* guile.texi (Memory Ports in Guile): Mark
	'memory-port-read-buffer-size',
	'set-memory-port-read-buffer-size!',
	'memory-port-write-buffer-size',
	'set-memory-port-read-buffer-size!' as deprecated.
	* doc/guile.texi (Guile Introduction): Clarify which Guile
	versions are supported.

Change-Id: Ib119b10a2787446e0ae482a5e1b36d809c44bb31