Update the pod for the recent identifier changes
toke.c: Stop parse_ident from punishing the non-utf8 case.

As a leftover from before the refactor, parse_ident was making
identifiers under 'no utf8;' go through the entire loop for each
character. Originally this way to stop it from glossing over
the [a-zA-Z]\p{XIDC} case, but since the utf8 check comes first
now, it's no longer needed; we can enter an inner loop until
there are no more WORDCHAR_A characters.
Simplify the rules for package delimiters.

This disallows multiple double colons (foo::::::bar) and following double
colons with a single quote (foo::'bar). This leaves TODO, which is disallowing
package Foo::;