Add a quit to maint_print_all_sections

If you have many sections, "maint print sections" can take a very long
time (due to a bug).  If you happen to "c" at the pagination prompt,
this can't be interrupted.  This patch adds a QUIT to the loop to at
least allow interruption.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32758
Reviewed-By: Guinevere Larsen <guinevere@redhat.com>