TYPO3 Core

After the basic bootstrap refactoring that moved the loading of ext_tables.php and
ext_localconf.php to class context, it is now easily possible to put the former
temp_CACHED_* files to the caching framework as cached PHP code, next to the
autoloader registry cache entry.

This patch introduces a new and clean API to t3lib_extMgm to handle the loading
of ext_localconf, ext_tables and the global TYPO3_LOADED_EXT array and removes
the current handling that was cluttered throughout the core.

The setting of TYPO3_CONF_VARS['SYS']['extCache'] is now deprecated and unused.
The bootstrap now decides based on its context, whether or not caching of those
files is used or not. This way we can for example now run the install tool in a
fully uncached environment and can get rid of the nasty side effects we had
in this area in the past.

With a simple call to ext_Mgm::removeCacheFiles() all cache entries in PHP code
cache that are tagged with 'core' can be removed at once. This currently affects
the autoloader registry, the TYPO3_LOADED_EXT entry, and the concatenated
ext_localconf and ext_tables files.

The patch furthermore gets rid of the _CACHEFILE array key in
$GLOBALS['TYPO3_LOADED_EXT'] that worked as a kind of API to the calling method to
indicate if a concatenated ext_tables and ext_localconf file is available.