SECURITY UPDATE: use-after-free in mod_http2 when file handles are
exhausted
debian/patches/CVE-2026-48913.patch: in c2_setup_io() in
modules/http2/h2_mplx.c, register the beam input callbacks
(h2_beam_on_send/received/consumed) only after the H2_USE_PIPES input
pipe has been created, so a pipe-creation failure under file-handle
exhaustion no longer leaves the callbacks referencing the torn-down
secondary (c2) connection. Backported from mod_http2 commit
d600b257c4714e43a2be8f5c9e1e5105f1d8f7ec (mod_http2 v2.0.40).