As no other polls for Tokyo touch the table of library headers,
I rebalanced the table columns.

Slight tweak to Annex C drafting when importing header units
to be consistent with previous wording --- the intent in LWG
was to match precedent.

This reformatting, in addition being consistent with the rest of
the clause, resolves an overful hbox warning.

Also added the missing text at end of the opening sentence
of p3.

The Annex C wording is modeled on the compatibility with C form,
and should be revised without the "difficulty of converting"
clause, probably with a simple code example in "Effects".

…late-head