Micro AIs: don't check for specific value of move rating

Don’t check whether rating equals (or doesn’t equal) -9e99 or the like,
verify that a valid move was found instead.  Also, avoid setting
variables to empty tables if not needed.
Restore instructions for VC dependencies
Fix CB-Scons target names
fix cb project file

First, rerverted changes starting with commit
09b0aad1f837353f80bb7319543053f5a9ae66a8, the other commits were
just fixups to that. The, manually went through the resulting diff
and added/removed files which I know of or think they actually should
be added/removed. And, of course, compiled and linked.
Add SDL2 specific files to VC project
Merge branch 'master' of https://github.com/aquileia/wesnoth into aquileia-master
SotBE S6: remove AI controller

It does not work with leaderless allied sides.
Update changelog