Remove dependency on psed for MSVC builds.

Remove dependency on psed for MSVC builds.

Modern Perl has removed psed from its core distribution, so it might not
be readily available on some build platforms. We therefore replace its
use with a Perl script generated by s2p, which is equivalent to the sed
script. The latter is retained for non-MSVC builds to avoid creating a
new hard dependency on Perl for non-Windows tarball builds.

Backpatch to all live branches.

Michael Paquier and me.