bug#12450: Remove configure's --without-sync-input option.

[Eli Zaretskii]

> Date: Sat, 15 Sep 2012 12:59:44 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> CC: 12450@debbugs.gnu.org, lekktu@gmail.com
> 
> Out of curiosity, what happens in MS-Windows if you take the
> current trunk and change nt/config.nt's "#undef SYNC_INPUT" to
> "#define SYNC_INPUT 1"?  If that works, it would help simplify the
> code overall.

I tried your patches already, they compile, and the resulting binary
seems to work.  But what does that prove?  Should I remind you that
another change installed recently took several days to reveal?

I hope Stefan will be able to add some real information to this issue.