Add lvalue pointer tests for Error* classes.
Reformat test execution summary printer.
Add benchmarks (enabled with --bench configure option).

Keep in mind that tests and the build are executed in parallel by default.
Benchmarks use the same mechanism as tests to execute themselves. So running
benchmarks with -j1 is recommended.
Simplify LICENSE file, no need to copy MIT license text twice.
Rewrite everything, use class_info structure.

Avoids as many lua api calls as possible. Ish. Just a try.