r2159: converted samba4 over to UTF-16.

r2159: converted samba4 over to UTF-16.

I had previously thought this was unnecessary, as windows doesn't use
standards compliant UTF-16, and for filesystem operations treats bytes
as UCS-2, but Bjoern Jacke has pointed out to me that this means we
don't correctly store extended UTF-16 characters as UTF-8 on
disk. This can be seen with (for example) the gothic characters with
codepoints above 64k.

This commit also adds a LOCAL-ICONV torture test that tests the first
1 million codepoints against the system iconv library, and tests 5
million random UTF-16LE buffers for identical error handling to the
system iconv library.

the lib/iconv.c changes need backporting to samba3
(This used to be commit 756f28ac95feaa84b42402723d5f7286865c78db)