The URL for the dist source repo changed
Bump version to 5.18.0-RC0

This was done with:

  ./perl -Ilib Porting/bump-perl-version -i 5.17.12 5.18.0

Followed by two tiny manual edits: INSTALL and patchlevel.h
regenerate uconfig.h and META.json
update perldiag with new warnings
put the perldelta we had been working on in place
remove the 5.17 deltas, update for 5.18
cleanup and test PERL_PERTURB_KEYS environment variable handling
document and improve hash algorithm randomization related build options

Install was a copy of other material, made heavy reference to 5.8.x and
and didnt really document what it should have. I reworked it to be more
up to date.
[perl #117791] Clarify that write does not match the C 'write' semantics
bump dist/IO/lib/IO/Handle.pm version to 1.34
pod/perldelta: Add in some deprecations; fix a typo

Feel free to improve the wording of these.
bisect-runner.pl: clarify -D,-U,-A args in docs

Based on http://www.perlmonks.org/?node_id=1032501, these arguments could
be confusing.
release_managers_guide: fix typo
INSTALL: fix a couple of typos
add various HASH defines to perl -V output

5.18 contains lots of new build knobs to control hash randomisation.
Add them to the perl -V output.
Restore the warning previously issued by (-l $fh)

This is a partial reversion of 433644eed8, which removed a
secondary, short-circuiting behavior when the warning was issued.

Now, the warning is issued, but the normal behavior (treat the
handle as a string) is maintained.  This work was done after
subsequent refactoring to doio.c, so it couldn't be just a
reversion with the "return" statement removed.
perldelta: document PERL_PERTURB_KEYS
perldelta: use Pod, not asterisks, for emphasis
perldelta: mention PERL_NO_INLINE_FUNCTIONS in delta
perldelta: mention non-blocking sockets on VMS