* Cleanup SP Cache code, now SP Cache only deletes sp_head objects in
sp_cache_flush_obsolete() invalidates all pointers to routines in the cache.
* Use new SP Cache use contract in the code.
There is no test case because it doesn't seem to be possible to cause thread races to end
the same way they end in heavy-load test. This patch removes the crash in heavy test.
* Don't activate prelocking mode for evaluating procedure arguments when it is not necessary.
* Code structure simplification and cleanup.
* Cleanup in .test files
its body, but lets each statement to get/release its own locks. This allows a broader set
of statements to be executed inside PROCEDUREs (but breaks replication)
This patch should fix BUG#8072, BUG#8766, BUG#9563, BUG#11126
New sp_cache C API. When an SP is dropped, old caches (in other threads)
become invalid and are cleared.
Also, the caches in THD are only created on demand.
