Problem: cppzmq build broken with C++11 compiler and git cloned repo.

Default build, ./ci_build.sh without any arguments, which causes to run
with draft disabled, does not work properly for git cloned repository and
C++11 compiler.

Two issues:
1. For git cloned repository ENABLE_DRAFTS is ON by default but libzmq
compiled build without drafts .Travis did not catch that because default build
runs on non C++11 compiler.
2. testutil.hpp does not build because of missing draft guards.

Solution 1: Remove check for presence of .git for enabling draft API as it
is confusing to use with ENABLE_DRAFTS flag and there should be only one
explicit way to enable draft build.

Solution 2: add missing draft guards in testutil.hpp for server/client
socket in use there.

Solution 3: add extra Travis build covering C++11 compiler and non
draft enabled build.

.travis.yml

@@ -30,7 +30,18 @@ matrix:
     # GCC default, draft disabled, default libzmq (defined in ci_build.sh)
     - os: linux
 
-    # GCC 7, draft enabled (default), latest libzmq (default)
+    # GCC 6, draft disabled (default), latest libzmq (default)
+    - os: linux
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-6
+      env:
+        - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
+
+    # GCC 7, draft enabled, latest libzmq (default)
     - os: linux
       addons:
         apt:

CMakeLists.txt

@@ -19,11 +19,7 @@ if (ZeroMQ_FOUND AND (NOT TARGET libzmq OR NOT TARGET libzmq-static))
   message(FATAL_ERROR "ZeroMQ version not supported!")
 endif()
 
-if (EXISTS "${CMAKE_SOURCE_DIR}/.git")
-    OPTION (ENABLE_DRAFTS "Build and install draft classes and methods" ON)
-else ()
-    OPTION (ENABLE_DRAFTS "Build and install draft classes and methods" OFF)
-endif ()
+OPTION (ENABLE_DRAFTS "Build and install draft classes and methods" OFF)
 if (ENABLE_DRAFTS)
     ADD_DEFINITIONS (-DZMQ_BUILD_DRAFT_API)
     set (pkg_config_defines "-DZMQ_BUILD_DRAFT_API=1")

tests/testutil.hpp

@@ -3,7 +3,7 @@
 #include <gtest/gtest.h>
 #include <zmq.hpp>
 
-#if defined(ZMQ_CPP11)
+#if defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11)
 #include <array>
 
 class loopback_ip4_binder