Copy stable/11@r303970 to releng/11.0 as part of the 11.0-RELEASE
cycle.

Prune svn:mergeinfo from the new branch, and rename it to RC1.

Update __FreeBSD_version.

Use the quarterly branch for the default FreeBSD.conf pkg(8) repo and
the dvd1.iso packages population.

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

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

When allocating memory, zero out them if we don't intend to overwrite them
all; before freeing memory, zero out them before we release it as free
heap. This will eliminate some potential information leak issue.

While there, remove the PURIFY option. There is a slight difference between
the new behavior and the old -DPURIFY behavior, with the latter initializes
memory with 0xff's. The difference between old and new approach does not
generate observable difference.

Obtained from: OpenBSD (partly).

Fix conflicts and merge into mainline