Remove unnecessary dropping of statement from cache for some errors

[anthony-tuininga]

Following on from issue #73,

And Btw. dpiStmt__execute function and performance. I found that all statements then returned error other than ORA-00001 get the deleteFromCache flag set. But for errors as 1400/1438/1461/2290/2291/2292/21525 one could also want not to drop the statements from OCI cache. Thought the "1" is the most common try&error case but similiar could apply to the other codes if application just tries the inserts/updates without previous validity checking and possibly deallocate the dpiStmt causing the deleteFromCache to apply before executing same statement with different values (which might not run into one of the errors).

I agree that these additional error codes should be added and the statement should not be removed from the cache if these errors occur. I'll add the code to make that happen.