manuals: Fix Fx and nearby mechanical typos

Fix compiler warnings related to the Fx macro, as well as all other
mechanical typos that were visible within one screenful of them. These
cause rendering glitches on various toolchains with various of the five
and a half decades of rich output formats and tooling manpages scale to.

The *x macro set specifies operating systems. These macros take the rest
of the line as an argument. Sometimes, a space was not used to separate
the argument of Fx and the trailing period. Another, FreeBSD Foundation
was misrepresented as an operating system version instead of an author.
Two more had other parts of the sentence supplied as an argument to Fx.

While I had those open, fix the other mechancial typos visible on those
specific screenfulls. Fix a list width glitch, correct section typo
AUTHOR to AUTHORS, and switch AUTHORS sections containing prose to
prose-mode so that they wrap freely when rendered.

PR: 297248
MFC after: 3 days
Fixes: d39e310c7d6a ("man/man3: add stdbit.3")
Fixes: d790b16bbf0c ("add man pages for stdbit functions")
Fixes: b61850c4e6f6 ("net.link.bridge.member_ifaddrs to false")
Reported by: wosch (groff is complaining about incorrect Fx usage)