Bump version numbers

These four core-only modules are about to be changed so that they call
av_tindex instead of av_len.  There's no chance that any of the version
numbers will need to be reverted, as we think that bumping a single-life
module's version is harmless.
Change av_len calls to av_tindex for clarity

av_tindex is a more clearly named synonym for av_len, available starting
in v5.18.  This changes the core uses to it, including modules in /ext,
which are not dual-lifed.
Change 'semantics' to 'rules'

The term 'semantics' in documentation when applied to character sets is
changed to 'rules' as being a shorter less-jargony synonym in this case.
This was discussed several releases ago, but I didn't get around to it.
Restore proper functioning of -Mdiagnostics

Commit 1c604e7c7f fixed some pod errors, but broke

./perl -Ilib -Mdiagnostics -e '$/=[]'

This fixes that.