bug#35062: [PATCH v3 2/3] constify a bit of xterm.c

[Eli Zaretskii]

> Cc: 35062@debbugs.gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Fri, 19 Apr 2019 17:31:38 -0700
> 
> 'const' is like 'register' in this respect. Putting 'const' nearly everywhere 
> clutters C code. It's pretty easy for a human reader to determine whether a 
> local variable is modified (if it's hard, write an Elisp function :-). In 
> hindsight, perhaps C should have been designed so that 'const' was the 
> default 
> for local variables; but the ship has sailed there too.

Thanks.  That was more or less my thinking as well.