We can't go to 3.0.1 yet as there are still build issues on
Linux and OSX. You can get Windows to build, but there's
still some display issues.
These changes should work with wxWidgets 2.8.12 as well, so
we can take our time to get things working properly before
switching over.
Replace the custom Makefile by automake. In addition drop the hacky
libwidgetextra-uninstalled.pc and configure the library like every other
optional library, but check if the library is not disabled.
