Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Back out addition of a plus sign.
DPADD and LDADD belong to individual makefiles.

:%s:\([A-Z][A-Z]ADD\)=:\1+=:g
Add the forgotten plus, which should unbreak the world build.

Upgrade to GNU texinfo 4.0

Bring back texindex from the dead. Some ports use it to format their docs.