Pre-existing code needs abstraction related cleanups.

[Yawning]

ngx_event_polarssl.[h,c] currently contains compatibility functions for the modules that make direct OpenSSL calls. The existing modules should be modified where possible so that the only place that directly calls the SSL implementation is ngx_event_[open,polar]ssl.[h,c].

[Yawning]

I'm not sure if I can totally fulfill this with what's required for #2 and #3. At least the Open/PolarSSL-isms will be neatly contained in #ifdefs.