Move OpenSSL initialization to a single place, make library usage thread-safe.

While doing some reading about OpenSSL, I noticed a couple of things that
needed to be improved with our usage of OpenSSL.

1) We had initialization of the library done in multiple modules.  This has now
   been moved to a core function that gets executed during Asterisk startup.
   We already link OpenSSL into the core for TCP/TLS functionality, so this
   was the most logical place to do it.

2) OpenSSL is not thread-safe by default.  However, making it thread safe is
   very easy.  We just have to provide a couple of callbacks.  One callback
   returns a thread ID.  The other handles locking.  For more information,
   start with the "Is OpenSSL thread-safe?" question on the FAQ page of
   openssl.org.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@205120 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_crypto.c

@@ -585,8 +585,6 @@ static struct ast_cli_entry cli_crypto[] = {
 /*! \brief initialise the res_crypto module */
 static int crypto_init(void)
 {
-	SSL_library_init();
-	ERR_load_crypto_strings();
 	ast_cli_register_multiple(cli_crypto, ARRAY_LEN(cli_crypto));
 
 	/* Install ourselves into stubs */