* src/nsterm.m ([EmacsSurface getContext]): Use BGRA for the IOSurface
and specify the CGContext explicitly for compatibility with a wider
range of Macs.

* src/nsterm.h:
* src/nsterm.m ([EmacsSurface initWithSize:ColorSpace:]): Objective C
init methods should init the superclass, and return id.

* src/nsterm.h: EmacsSurface is only required if NS_DRAW_TO_BUFFER is
defined.
* src/nsterm.m (ns_judge_scroll_bars): Remove unused variable.
* src/nsmenu.m (update_frame_tool_bar):
(ns_update_menubar): Remove unused variables.

* src/nsterm.h: New EmacsSurface class and update EmacsView
definitions.
* src/nsterm.m ([EmacsView dealloc]):
([EmacsView viewDidResize:]): Handle new EmacsSurface class.
([EmacsView initFrameFromEmacs:]): Remove reference to old method.
([EmacsView createDrawingBuffer]): Remove method.
([EmacsView focusOnDrawingBuffer]):
([EmacsView unfocusDrawingBuffer]):
([EmacsView windowDidChangeBackingProperties:]): Use new EmacsSurface
class.
([EmacsView copyRect:to:]): Get information from the context instead
of direct from the IOSurface.
([EmacsView updateLayer]): Use new EmacsSurface class.
([EmacsSurface initWithSize:ColorSpace:]):
([EmacsSurface dealloc]):
([EmacsSurface getSize]):
([EmacsSurface getContext]):
([EmacsSurface releaseContext]):
([EmacsSurface getSurface]):
([EmacsSurface copyContentsTo:]): New class and methods.

* src/nsterm.m ([EmacsView copyRect:to:]): Use memcpy to copy bits
around instead of using NS image functions.

* configure.ac: Require IOSurface framework.
* src/nsterm.h: Add new definitions.
* src/nsterm.m (ns_update_end):
(ns_unfocus): Use new unfocusDrawingBuffer method.
(ns_draw_window_cursor): Move ns_focus to before we set colors.
([EmacsView dealloc]): Release the new IOSurface.
([EmacsView createDrawingBuffer]): Use a new IOSurface to draw to
and point a CGBitmapContext to it.
([EmacsView focusOnDrawingBuffer]): Lock the IOSurface for drawing.
([EmacsView unfocusDrawingBuffer]): New function.
([EmacsView updateLayer]): Use the IOSurface.

* src/doc.c (get_doc_string, Fdocumentation)
(Fdocumentation_property, store_function_docstring):
Minor cleanup.

* src/process.c (Fmake_serial_process): Add port to error data.
(connect_network_socket): Add an explanatory comment.

This works even if another thread or process resets the resource limit
for open file descriptors, e.g., using 'prlimit' on GNU/Linux.

* src/process.c (create_process, create_pty, Fmake_pipe_process)
(Fmake_serial_process, connect_network_socket)
(server_accept_connection): Limit file descriptors to FD_SETSIZE.
* test/src/process-tests.el (process-tests--with-raised-rlimit): New
helper macro.
(process-tests--fd-setsize-test): Rename from
'process-tests--with-many-pipes'.  Increase resource limit during test
if possible.
(process-tests/fd-setsize-no-crash/make-process)
(process-tests/fd-setsize-no-crash/make-pipe-process)
(process-tests/fd-setsize-no-crash/make-network-process)
(process-tests--new-pty): Rename callers.

Previously this was only checked in a few places.  Now assert that
file descriptors are within the expected range whenever we'd otherwise
introduce undefined behavior.

* src/process.c (add_read_fd, add_process_read_fd, delete_read_fd)
(recompute_max_desc, delete_write_fd, compute_input_wait_mask)
(compute_non_process_wait_mask, compute_non_keyboard_wait_mask)
(compute_write_mask, clear_waiting_thread_info)
(update_processes_for_thread_death, Fset_process_thread)
(create_process, create_pty, Fmake_pipe_process)
(Fprocess_datagram_address, Fset_process_datagram_address)
(Fmake_serial_process, finish_after_tls_connection)
(connect_network_socket, deactivate_process)
(server_accept_connection, wait_reading_process_output)
(read_process_output, read_and_dispose_of_process_output)
(send_process, Fcontinue_process, Fprocess_send_eof)
(Fprocess_filter_multibyte_p, keyboard_bit_set)
(add_timer_wait_descriptor, setup_process_coding_systems): Add
assertions to document and check that file descriptors are within the
expected range when used as file descriptor set elements or array
subscripts.