Check for OpenSSL defines before trying to use them.

The SSL_OP_NO_TLSv1_1 and SSL_OP_NO_TLSv1_2 defines did not exist prior
to OpenSSL version 1.0.1. A recent commit attempts to, by default, set
these options, which can cause problems on systems with older OpenSSL
installations.

This commit adds a configure script check for those defines and will not
attempt to make use of those if they do not exist. We will print a
warning urging the user to upgrade their OpenSSL installation if those
defines are not present.

Change-Id: I6a2eb9a43fd0738b404d8f6f2cf4b5c22d9d752d

configure.ac

@@ -2302,6 +2302,12 @@ then
         AST_C_DECLARE_CHECK([OPENSSL_ECDH_AUTO], [SSL_CTX_set_ecdh_auto], [openssl/ssl.h])
 fi
 
+if test "$PBX_OPENSSL" = "1";
+then
+        AST_C_DEFINE_CHECK([SSL_OP_NO_TLSV1_1], [SSL_OP_NO_TLSv1_1], [openssl/ssl.h])
+        AST_C_DEFINE_CHECK([SSL_OP_NO_TLSV1_2], [SSL_OP_NO_TLSv1_2], [openssl/ssl.h])
+fi
+
 AST_EXT_LIB_CHECK([SRTP], [srtp], [srtp_init], [srtp/srtp.h])
 
 if test "$PBX_SRTP" = "1";