Travis: The TLS 1.3 code isn't interoperable yet, move it to its own build

We should move it back to the BORINGTEST build when we are approaching
interoperability.
Reviewed-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2123)

.travis.yml

@@ -42,7 +42,7 @@ matrix:
           env: CONFIG_OPTS="--strict-warnings no-deprecated" BUILDONLY="yes"
         - os: linux
           compiler: gcc-5
-          env: CONFIG_OPTS="--debug --coverage no-asm enable-tls1_3 enable-rc5 enable-md2 enable-ec_nistp_64_gcc_128 enable-ssl3 enable-ssl3-method enable-nextprotoneg enable-weak-ssl-ciphers enable-external-tests no-shared -DPEDANTIC -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION" COVERALLS="yes" BORINGSSL_TESTS="yes" CXX="g++-5"
+          env: CONFIG_OPTS="--debug --coverage no-asm enable-rc5 enable-md2 enable-ec_nistp_64_gcc_128 enable-ssl3 enable-ssl3-method enable-nextprotoneg enable-weak-ssl-ciphers enable-external-tests no-shared -DPEDANTIC -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION" COVERALLS="yes" BORINGSSL_TESTS="yes" CXX="g++-5"
         - os: linux
           compiler: clang-3.6
           env: CONFIG_OPTS="enable-msan"
@@ -55,6 +55,9 @@ matrix:
         - os: linux
           compiler: gcc-5
           env: CONFIG_OPTS="no-asm enable-ubsan enable-rc5 enable-md2 -DPEDANTIC"
+        - os: linux
+          compiler: gcc-5
+          env: CONFIG_OPTS="--strict-warnings enable-tls1_3" COMMENT="Move to the BORINGTEST build when interoperable"
         - os: linux
           compiler: i686-w64-mingw32-gcc
           env: CONFIG_OPTS="no-stdio" BUILDONLY="yes"