Refactor + reorganize openssl files

- All streams-related code now lives in xp_ssl.c. Previously stream
  code was split across both openssl.c and xp_ssl.c
- Folded superfluous php_openssl_structs.h into xp_ssl.c
- Server options now set on SSL_CTX instead of SSL
- Deprecate SNI_server_name ctx option
- Add SNI_server_certs ctx option for server-side SNI support
- Miscellaneous refactoring
Raise timeout to 2s, reworded ssl timeout warning