Add IgnoreNull flag to WrappedInputCString, analogous to the IgnoreNull flag in
WrappedOutputCString.
Add SimpleWrapper-based interception functions for setlocale and localeconv.

The interception function for localeconv() uses a custom return state recorder
which, as well as recording the state of the static lconv that is referenced
by the returned pointer, records the state of all C strings referenced by the
members of that lconv.