2) Replaced "early" (before LM) checkouts with "late" (inside LM) ones.
3) Removed the mutex protection that's no longer necessary.
Note: the new LM contains some future code (currently commented out) which will be enabled and tested after the Alpha release.
1) Make memory counters aggregated.
2) Add attachment pool and allocate appropriate resources out of this pool.
3) Always release attachments explicitly (via destructor).
4) Always delete user requests prior to attachment deletion.
5) Introduce memory usage counters per every monitoring object.
6) Misc refactoring.
Some pieces are still incomplete (although everything basically works), but I'd like to get feedback and testing sooner rather than later.
2) Remove internal y-valve function INTERNAL_COMPILE_REQUEST
3) Go direct to engine internals from DSQL, without need to exit/enter the attachment lock and check exceptions in status vector
