[Mono-list] New CultureInfo support

[Dick Porter]

I've just checked in the majority of the new CultureInfo support.  It
relies on IBM's libICU to do the actual work, though this new dependency
is a compile-time option (if you don't have the library, you only have
the Invariant locale available.)

The ICU (International Components for Unicode) library gives us full
language-sensitive collation and searching, and locale data.  (It has
lots of other Unicode support features, but we don't use them yet.)  It
is available from http://oss.software.ibm.com/icu under an X-style
licence.  The library is known to work on Linux, AIX, HPUX, Solaris and
Windows platforms.

- Dick