Convert the codebase to PHP 5.3 namespaces

Attention: This means code relying on classes being available in the
global namespace will break. For example: new Date() will not work
any longer, instead one will have to write new \util\Date() or use
the "use" statement to import it. Only the classes in the "lang"
package and its subpackages are created with aliases in the global
namespaces.

The codebase is not yet completely tested, there are most probably
some migration leftovers causing problems. It has been fixed up to
pass the core testsuite, however:

$ unittest src/test/config/unittest/core.ini
[...]
OK: 1205/1227 run (22 skipped), 1205 succeeded, 0 failed
Memory used: 9280.51 kB (9797.01 kB peak)
Time taken: 1.186 seconds
Remove superfluous mappings
Fix various instances of incorrectly migrated class names
E.g. inside newinstance() or defineClass(), but also in other
situations not so clearly traceable.
Remove bootstrap debugging code
Fix class names inside peer API
Fix class names inside text.regex API
Register "crc16"
Previously done by uses(), now need to load explicitely
Fix missing io.streams references
Fix test expectancies
Fix class names inside util API