This reverts commit e387371497d313f05b94e3bf42fe6685184605d1.

* src/image.c (svg_load): Use ENCODE_FILE for `:base-uri'

* doc/lispref/display.texi (SVG Images): Add more documentation for
  `:base-uri'

b242bbb073 (origin/emacs-27) ; lisp/org/org.el: Fix Version header.
e0fc939c5f Add more details to the "word processor" section
fda9b3e83a * src/Makefile.in (DO_CODESIGN): Fix expected architecture...

This reverts commit 2c79a8f9210db01c86b0e5f236adeb0509519d30.
It breaks the MinGW build in too many ways, and should be
first tested on a branch.

posix_spawn is less error-prone than vfork + execve, and can make
better use of system-specific enhancements like 'clone' on Linux.  Use
it if we don't need to configure a pseudoterminal.

* src/Makefile.in (LIB_POSIX_SPAWN): New variable.
(LIBES): Use it.

* src/callproc.c (emacs_spawn): Use posix_spawn on Unix-like system if
we don't need to set up a pseudoterminal.

The latest Gnulib merge brought in free-posix, which causes 'free'
to preserve errno.  This lets us simplify some Emacs code that
calls 'free'.
* admin/merge-gnulib (GNULIB_MODULES): Add free-posix.
This module is pulled in by canonicalize-lgpl anyway,
so we might as well rely on it.
* lib-src/emacsclient.c (get_current_dir_name):
Sync better with src/sysdep.c.
* lib-src/etags.c (process_file_name, etags_mktmp):
* lib-src/update-game-score.c (unlock_file):
* src/fileio.c (file_accessible_directory_p):
* src/sysdep.c (get_current_dir_name_or_unreachable):
Simplify by assuming that 'free' preserves errno.
* src/alloc.c (malloc_unblock_input):
Preserve errno, so that xfree preserves errno.
* src/sysdep.c (get_current_dir_name_or_unreachable):
Simplify by using strdup instead of malloc+memcpy.
No need for realloc (and the old code leaked memory anyway on
failure); just use free+malloc.

* src/gtkutil.c (xg_item_label_same_p): Simplify.  Without this
simplification, GCC (Ubuntu 10.2.0-13ubuntu1)
-Wanalyzer-null-argument complains about use of NULL where
non-null expected as argument of strcmp.

* src/w32.h (set_process_dir):
* src/w32proc.c (set_process_dir): Change the argument to 'const
char *'.
* src/lisp.h (make_environment_block):
* src/callproc.c (make_environment_block): Now returns 'char **'.
(exec_failed) [DOS_NT]: Remove unused function.
* src/callproc.c (child_setup): NEW_ARGV and ENV are now 'char **'.
Making them 'const' breaks the MinGW build and is not needed for
other platforms.
* src/callproc.c (emacs_spawn): ARGV and ENVP arguments are now
'char *', for the same reason.
* src/process.c (create_process): Adapt to above changes.

Getting the vfork + execve combination right isn't easy, and the code
was partially duplicated between callproc.c and process.c.  Centralize
the spawn operation in a single function that deals with the nasty
details.  Going forward, we should be able to use posix_spawn from
either libc or Gnulib (or CreateProcessW on Windows) in the non-pty
case.

* src/callproc.c (emacs_spawn): New function to start an asynchronous
subprocess.  Merge code from 'call_process' and 'create_process' into
this function.
(call_process): Use new 'emacs_spawn' function.
(child_setup): Make static, since there are no users outside this
compilation unit left.
(CHILD_SETUP_TYPE): Move from header file, since there are no users
outside this compilation unit left.

* src/process.c (create_process): Use new 'emacs_spawn' function.