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
> 
> >> -#ifdef REL_ALLOC
> >> -  malloc_hysteresis = 32;
> >> -#else
> >> -  malloc_hysteresis = 0;
> >> -#endif
> 
> malloc_hysteresis is used only by the non-SYNC_INPUT code.

No, it is also used indirectly, via __malloc_extra_blocks, in
gmalloc.c and in ralloc.c.  Since only one platform I know of that
uses SYNC_INPUT also uses ralloc.c, I'm not sure it's safe to make
this change to __malloc_extra_blocks.

But there's something I don't understand about this snippet.  Why does
it set the value to 32 conditioned by REL_ALLOC, and just a few days
after the change which introduced this snippet (18 years ago) there
was a change committed in ralloc.c that overrides the value of
__malloc_extra_blocks with 64?  If using ralloc.c always sets
__malloc_extra_blocks to 64, why setting it to 32 in alloc.c is
conditioned by REL_ALLOC?

Richard, you made both changes -- can you perhaps shed some light on
this?