Second part of fix for bug 8310 - toupper_ascii() is broken on big-endian systems.

Second part of fix for bug 8310 - toupper_ascii() is broken on big-endian systems.

Re-add:
    smb_ucs2_t toupper_w(smb_ucs2_t v);
    bool isupper_w(smb_ucs2_t v);
    smb_ucs2_t tolower_w(smb_ucs2_t v);
    bool islower_w(smb_ucs2_t v);

and ensure they are called whenever we are operating on smb_ucs2_t
variables. I'd like to make the definition of smb_ucs2_t incompatible
with int and codepoint_t so they can't be mixed, but that's a patch
for another time.
(cherry picked from commit bdc078a81e49bce3b51560a75984e0306c387573)