[patch, rfc] Don't try to build printcmd.c and valprint.c with -Wformat-nonliteral

[Andrew Cagney]

> Comments, thoughts, anyone want to overhaul the language output format 
> ac> code?  The other option is to wind back the -Werror list, sigh.
> 
> Meta-comments from the peanut gallery:
> 
> What a great "-W" switch, it is finding multiple real bugs.

Yes.  Like the others, it's flushing out problems.  Over time people 
forget how bad things get without such switches / cleanups.

> I'm happy with the path you are following: file one PR for each source
> file found, then remove -Werror from that source file.  As the PR's
> get fixed then the Makefile hacks can be rolled back.
> 
> I'd be happy to work on those PR's in the fullness of time.

For valprint, there is already a todo PR of overhaul the language format 
code.  A few more related TODO's will help dump the priority :-)

Andrew