warnings from MacOS clang

[arnold]

Hi.

I got the below from one of my testers. If y'all feel like updating the
relevant files in GNULIB, that'd be great. If instead you feel like,
well, to heck with that, that's also OK. :-)

Thanks,

Arnold

> From: Pat Rankin <r.pat.rankin@gmail.com>
> Date: Mon, 10 May 2021 18:13:33 -0700
>
> > https://www.skeeve.com/gawk/gawk-5.1.1c.tar.gz
>
> OSX 10.11.6
> Building after using 'touch .developing' for the first time, I get
>
> depbase=`echo dfa.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
> gcc -DGAWK -DHAVE_CONFIG_H -I"./.." -I. -I..   -I/opt/local/include
> -I/opt/local/include -g -O2 -DARRAYDEBUG -DYYDEBUG -DLOCALEDEBUG
> -DMEMDEBUG -Wall -fno-builtin -g3 -ggdb3 -g -O2 -DARRAYDEBUG -DYYDEBUG
> -DLOCALEDEBUG -DMEMDEBUG -Wall -fno-builtin -g3 -ggdb3 -MT dfa.o -MD
> -MP -MF $depbase.Tpo -c -o dfa.o dfa.c &&\
> mv -f $depbase.Tpo $depbase.Po
>
> dfa.c:1627:19: warning: suggest braces around initialization of subobject
>       [-Wmissing-braces]
>   mbstate_t s = { 0 };
>                   ^
>                   {}
> 1 warning generated.
>
> Also two similar warnings from localinfo.c, lines 47 and 103.
> [Note: despite being invoked as 'gcc' the compiler is 'clang'
> and not a particularly recent version.]
>
> Even with warnings, the build completed successfully.
> All tests passed.
>