…lso very importantly memory fragmentation).

Added StringCache.pas.
Changed attributes to use the string cache.
Note required a define USESTRINGCACHE which is off by default. The cache is not threadsafe.

…ionary of attributes, but attributes no longer work as a dictionary.)

…en threadsafe, any individual instance has get/add method contents wrapped in a lock, to lock the internal structures. The instance is never cleared when the count of objects using it drops to 0, since that's a bit more complex to get right (should only clear while the refcount is 0, but have to lock that to ensure it's not changed while clearing is happening, which severely slows inc/decrementing the count. I couldn't think of a good compare-lock-exchange algorithm. So just don't bother; it's never cleared while alive, when threadsafe.)

…both operations; now holds it for both. Safe to enter a CS twice.)

This reverts commit 95233e9.