Doc++
Include configure.h from Corrade.h.

So the user really gets all configured preprocessor variables when
including <Corrade/Corrade.h>, as stated in many places in the docs.
doc: crosslink preprocessor variables with CMake documentation.
Doc++
Updated toolchains submodule.
package: adapt Emscripten PKGBUILD to emscripten-git AUR package.
Oh Doxygen you so predictable.
doc: make section headers in class docs have sane size.

The \section Doxygen command has unnecessarily large font size when used
in class documentation, it is even bigger than the "Detailed
Description" header, which looks very ugly.

Using \subsection doesn't help, as Doxygen then complains about
\subsection without enclosing \section. Worked around that by using
Markdown `##` syntax and adding \anchor where needed. Also prefixed the
\anchor with namespace to make the identifier really unique.
package: removed MinGW32 Jenkins CI build.

I don't have this on my system anymore, so there's that. Another step in
dropping the support completely.
package: build also tests in MinGW-w64 PKGBUILD.

Just to be sure that everything works.
Utility: fixed Android build.
package: added Android Jenkins CI configuration.