Maybe we should also rename "opt" to "trans" in the future...

This is necessary because the walker does not guarantee that all Projs
of the second Tuple are visited after we optimized the first Tuple.

It has been empty for nearly all systems. People who used to put stuff
in config.h can still create a config.h on their own and inject
-include (gcc) or /FI (msvc) into their CPPFLAGS.

Just state the copyright and the project the files belong to. You can
then find the COPYING file for the whole project.

The opt_manage framework didn't really do much except assuring that some
analysis info is computed before a pass starts. We can achieve this
simpler by providing an assure_irg_properties function.
This commit also fixes some places where analysis info was potentially
not invalidated before.

Noone was really using the return values anyway. This change makes the
API more consistent.

public functions are already documented in their headers, no need to
repeat the comment at the definition site.