constant.pm: Rmv ref in pod to non-existent module
podcheck.t: Note existence of some CPAN modules
Tie/File.pm: Fix pod broken link typo
Math-BigInt: Fix some broken links
libnetcfg.PL: Fix broken pod link
Math/BigRat.pm: Fix some broken pod links

This also changes the link to blog() to an internal one; it remains
broken, but should be documented in this pod, not outside it
dist/bignum/lib/bigint.pm: Fix broken pod link
dist/bignum/lib/bigrat.pm: Fix broken pod link
ext/Pod-Html/testdir/perlvar-copy.pod: Fix broken pod links
dist/bignum/lib/bignum.pm: Fix broken pod link
Add Felipe Gasper to AUTHORS
emphasize signal names over numbers in kill() docs
update ExtUtils-MakeMaker to github v6.65_01

Perl core specific highlights:
* Fix hash related issues for 5.18.
* Do not hard code the list of perl header files - discover them from disk instead
* Don't need completely different include file collector on VMS.
add a "hash quality score" to Hash::Util::bucket_stats()
Split out hash functions into new file and turn into inline static functions

This includes various tweaks related to building SipHash and other
cleanup.
add a hardened one-at-a-time hash variant

Mix in additional randomness into the final value.
silence signed mistmatch in comparison warning in Murmurhash

as far as I can tell 'i' can only be positive here.
default to PERL_FUNC_ONE_AT_A_TIME_HARD for all builds

For testing, but maybe for ever
rework ROTL definitions (and add ROTL_UV)
Harden hashes against hash seed discovery by randomizing hash iteration

Adds:

S_ptr_hash() - A new static function in hv.c which can be used to
hash a pointer or integer.

PL_hash_rand_bits - A new interpreter variable used as a cheap
provider of "semi-random" state for use by the hash infrastructure.

xpvhv_aux.xhv_rand - Used as a mask which is xored against the
xpvhv_aux.riter during iteration to randomize the order the actual
buckets are visited.

PL_hash_rand_bits is initialized as interpreter start from the random
hash seed, and then modified by "mixing in" the result of ptr_hash()
on the bucket array pointer in the hv (HvARRAY(hv)) every time
hv_auxinit() allocates a new iterator structure.

The net result is that every hash has its own iteration order, which
should make it much more difficult to determine what the current hash
seed is.

This required some test to be restructured, as they tested for something
that was not necessarily true, we never guaranteed that two hashes with
the same keys would produce the same key order, we merely promised that
using keys(), values(), or each() on the same hash, without any
insertions in between, would produce the same order of visiting the
key/values.