Memory leak with statements (dpiConn_prepareStmt()).

[jaman]

I've been working to try to find a memory leak in oranif, and believe I've found it.
I hit the leak as I hit 50+ databases every five seconds or so. This makes the leak jump out, as it grows 160 bytes per query.

The leak is in that the dpiConn_prepareStmt() is called, along with dpiStmt_close, but never the dpiStmt_release().
Without the release, the 160 bytes of the prepared statement stays around, unused, and uncleared for each query.
In my copy of oranif, I've added a dpiStmt_release(stmtRes->stmt); after the dpiStmt_close call (line 419 of dpiStmt_nif.c).

This looks to have possibly rectified memory issues in my environment, though I'll be testing for the next couple of days to see if I run into the memory leak over time.