dns/dnsmasq-devel: update to v2.91rc5

Upstream changes since rc4, all by Simon Kelley:

• 5990074 2025-02-21 | Fix stupid error in allocating 0x20-flip bitmaps.
• d17581c 2025-02-21 | Use correct packet length when 0x20 flipping truncated packet.
• 2c9ed7f 2025-02-20 | Fix possible problems with case-encode bigmap array allocation.
• 717ff6a 2025-02-10 | Update plen when getting retried query from stash.

MFH: 2025Q1
(cherry picked from commit 05d61c2eda9fdff5d9789502507718c282ff0fec)