print/cups: Fix regressions

• Apply upstream patch to unblock GTK+ print dialogs.
• Apply upstream patch for out-of-bounds read in cupsUTF8ToCharset().
• Make cupsd ignore IdleExitTimeout in cupsd.conf.

Reported by: christos

(cherry picked from commit 773bd2e7b1a41da404618d926804350768223e7f)