[Libreoffice] New tinderbox: MinGW cross-compilation

[Tor Lillqvist]

>   - enable & fix pieces that are currently disabled

In addition to those kendy mentioned, off the top of my head:

- none of the custom actions of the MSI installer are built; I don't recall the exact reason for this, it might be that the necessary headers and import libraries actually are available after all and these could be built. (I think it was so that MinGW didn't come with an import library for msi32.dll, but later I found the corresponding .def file in Wine, we now have a copy in external/wine, so we actually could probably build them. Of  course, whether we need such custom actions in the MSI installer depends on whether we are able to build such an installer when cross-building in the first place, or whether we do a NSIS-based one, or something else...

- the shell (Explorer) extension (shell/source/win32/shlxthandler). requires headers (and import libraries) not present in MinGW and not in Wine either, IIRC

--tml