Funcsynopsisinfo must be handled as a verbatim.

Funcsynopsisinfo must be handled as a verbatim.
Problem:: Existing code was not preserving breaks and whitespace
in Funcsynopsisinfo. Cause:: Lack of awareness that
Funcsynopsisinfo is a verbatim environment. Fix:: Handle in
Funcsynopsisinfo in the same way as other verbatims (that is,
wrap in .nf/.fi requests. Additional problem: According to man(7)
man page and existing man2/ pages, all parts of a funcsynopsis
that are not args must be in bold. But because Funcsynopsisinfo
is a verbatim, it needs different roff bold markup than other
stuff. So wrapped it in ".ft B"/ft pair. (Perhaps it might make
sense to wrap the whole funcsynopsis in ".ft B"/ft instead of
trying to bold/unbold at the word level, as we are doing now. Or
perhaps not.)

Closes bug #1447121. Thanks to Joe Orton for reporting.