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

main/asterisk.c

@@ -3571,6 +3571,11 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
+	if (ast_ssl_init()) {
+		printf("%s", term_quit());
+		exit(1);
+	}
+
 #ifdef AST_XML_DOCS
 	/* Load XML documentation. */
 	ast_xmldoc_load_documentation();