* 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.

This matches the signature of execve.

* src/callproc.c (child_setup): Declare NEW_ARGV as char *const *.

This avoids the impression that 'child_setup' could do anything
Lisp-related.

* src/callproc.c (child_setup): Pass C pointer to current directory
name.
(call_process): Adapt callers.

* src/process.c (create_process): Adapt callers.

While 'child_setup' carefully avoids calls to async-signal-unsafe
functions like 'malloc', it seems simpler and less brittle to use
normal allocation outside the critical section between 'fork' and
'exec'.

* src/callproc.c (make_environment_block): New function to create the
environment block for subprocesses.  Code largely extracted from
'child_setup' and adapted to use 'xmalloc' instead of 'alloca'.
(child_setup): Remove environment block allocation in favor of
passing the environment block as command-line argument.
(call_process): Adapt to new calling convention.

* src/process.c (create_process): Adapt to new calling convention.

* src/callproc.c (child_setup): Remove unused SET_PGRP parameter.

* src/callproc.c (call_process):
* src/process.c (create_process): Fix all callers.

32090a3de4 Improve documentation of streams in batch mode
34feded008 Support ks_c_5601-1987 encoding
da00a6f317 Fix Xaw widget text disappearing when built with cairo (bu...
6916e7954a Improve documentation of 'ps-print-color-p'
6663b2f211 ; * lisp/simple.el (move-beginning-of-line): Doc fix.
a4dd03ebe9 ; * src/charset.c (Fmap_charset_chars): Doc fix.
d86cc3ffcb ; * src/chartab.c, src/lisp.h: Fix typos in comments.

* src/xdisp.c (clear_message_stack): New function.
* src/emacs.c (terminate_due_to_signal): Call clear_message_stack
when we are being shut down by SIGINT under -batch.
* src/lisp.h (clear_message_stack): Add prototype.