Firefox 117 on POWER

Now that the Talos II is upgraded and tuned up, it's back to development work, starting with (after a TenFourFox patch dump) Firefox 117. Maybe it's just me, but it seems subjectively zippier than 116, even accounting for the cruft that builds up during long browser sessions, and there are some notable developer-facing improvements. As usual, for the long-playing bug 1775202, either put --disable-webrtc in your .mozconfig if you don't need WebRTC, or tweak third_party/libwebrtc/moz.build with the patch from Fx116. The browser otherwise builds and works with a tweaked PGO-LTO patch and the .mozconfigs from Firefox 105.