EBCDIC sanity - phase I

EBCDIC sanity - phase I
 - rename utf8/uv functions to indicate what sort of uv they provide (uvuni/uvchr)
 - use utf8n_xxxx (c.f. pvn) for forms which take length.
 - back out vN.N and $^V exceptions to e2a/a2e
 - make "locale" isxxx macros be uvchr (may be redundant?)

Not clear yet that toUPPER_uni et. al. return being handled correctly.
The tr// and rexexp stuff still needs an audit, assumption is they are working
in Unicode space.

Need to provide v5.6 names for XS modules (decide is uni or chr ?).

p4raw-id: //depot/perlio@9096