Account for grouping in printf width (bug 30068)

This is a partial fix for mishandling of grouping when formatting
integers.  It properly computes the width in the presence of grouping
characters when the width is larger than the number of significant
digits. The precision related issue is documented in bug 23432.

Co-authored-by: Andreas Schwab <schwab@suse.de>
(cherry picked from commit c980549c)