HTML tags must be uppercase

[Kohei Yoshida]

Just FYI,

http://cgit.freedesktop.org/libreoffice/core/commit/?id=3d481254a07fe82d11953f9825a2f8fc6eeabc0b

we need to stick with uppercased HTML tags because using lower-cased
tags apparently breaks Windows clipboard functionality.

https://bugs.freedesktop.org/show_bug.cgi?id=74584
https://bugs.freedesktop.org/show_bug.cgi?id=74537

No idea why lower-cased html tags won't work there, but the condition
appears to be indepdent of applications.  I've tested Word, Excel and
Firefox, and the bug reporters have tested several others such as Google
Chrome and Thunderbird.

The 4.2 backport request is pending here:
https://gerrit.libreoffice.org/#/c/8132/

Kohei