Task #40095: Move core to namespaces
Remove compatibility layer of new classes in 6.0
There is no compatibility layer needed for classes that were added
with 6.0. This first patch affects the whole lots of classes in t3lib/,
especially some new 6.0 cache classes, the category collection and
the whole FAL layer. The compatibily files are removed, deleted from
core_autoload and the migration class_alias file and all other
occurences of the class names within the core are cleaned up.