MFH: r525179

www/firefox: apply upstream powerpc64 fixes

Many of these are stalled on review for various reasons but the intent
of each seems clear enough to keep rebasing or ask upstream for help.
pkg-fallout@ would identify rebase mistakes while atomic changes would
identify when a particular patch is no longer useful.

Submitted by: mikael (via D21765)
Approved by: ports-secteam blanket