Fix moderncv include for "headxlii" and friends.

Fix moderncv include for "headxlii" and friends.

The fix for https://github.com/xdanaux/moderncv/issues/1, namely
https://github.com/xdanaux/moderncv/commit/c91b6ca77c7fe422f8519a433d13db6c3c715384,
switched the \moderncv{head,body,foot} macros from using \romannumeral,
which operates on at least a large number of counting numbers, to just
handling numbers 1 through 10.

Notably, 42 and 43 are outside that range, so just minimally fix this up
by doing a few rounds of macro expansion by hand and directly using
\RequirePackage ourselves.  And since we're doing that, there's no need
to use a number, so move to something that won't clash with upstream
moderncv.