remove the perl519*delta documents
update perlhist for v5.20.0
patchlevel: we are now v5.20.0-RC1
PATCH: [perl #121630]: perlpod clarification
perlfunc: Should chdir("/") immed after chroot

Inspired by Coverity perl5 CID 28931: Insecure chroot: (CHROOT)
chroot_call.

The Perl chroot() is a thin wrapper around the system call, so the
chdir("/") should not go there.  But adding a note about the chdir()
being a good idea to perlfunc/chroot.

The committer reworded the inserted text for grammar and readability,
and the commit message to conform to git standards, and is pushing the
commit with the concurrence of the author.
perldelta: update known problems
perldelta: Note patch fixed a bunch of tickets

Unbeknownst to the authors, several other tickets got fixed.
Add notice for removal of find2perl, s2p and a2p
Note that the minimum supported gcc (on Windows) is 3.4.5

Earlier versions (from www.mingw.org, at least) will build perl, but have
a linker bug that causes various tests to fail due to problems with
SDBM_File.dll. See perl #121936 for details.
Document known test failure in www.mingw.org builds of gcc-4.8.1 (at least)

This came up in perl #121643, but I forgot to add a note of this Known
Problem.