bug#29183: 27.0.50; SIGSEGV on C-g on Windows

[Eli Zaretskii]

> From: John Mastro <john.b.mastro@gmail.com>
> Date: Mon, 6 Nov 2017 13:58:30 -0800
> 
> On master (at commit 1d8f885) on 64-bit Windows 10 I get a SIGSEGV as
> soon as I hit C-g. Just "emacs -Q; C-g" is enough to trigger it.
> 
> I've attached the output of a GDB session with "bt full" ("xbacktrace"
> didn't print anything). Please let me know if I can provide any further
> information.
> 
> I tried to reproduce the error with an -O0 build, but it doesn't occur
> then. The backtrace is from an -O2 build.

Is this again bug#29040?  Did main_thread become mis-aligned again?