Setup ABI tracker

[abooij]

There are at least two reasons we are interested in implementing libwayland's ABI:

1. It makes sudbury into a drop-in replacement of libwayland.
2. If somebody wants to write a compositor with sudbury, then the (e.g.) EGL libraries that they'll want to use expect to be able to call back into libwayland.

Simply taking the relevant C header files and writing appropriate "foreign export" statements seems to work very well. But for correctness and completeness it would be useful to have a tool that constantly monitors the differences of the libwayland and sudbury ABI.

Google turns up "ABI Compliance Checker" and "abidiff" which look relevant, but I did not look into it much.

An added challenge here will be that sudbury's versions of the libraries will expose a lot of extra symbols that come with the Haskell runtime. These should be filtered out of the report.