Restored CMake 2.8.11 minimum version

Popular and modern Linux distribuitions have CMake 2.8.12
(sometimes 2.8.11). So these version must be supported. For this use
old FindCXX11 find module to get correct compiler flags.

CMakeLists.txt

@@ -9,10 +9,18 @@ set(TUFAO_VERSION ${TUFAO_VERSION_MAJOR}.${TUFAO_VERSION_MINOR}.${TUFAO_VERSION_
 set(TUFAO_BRIEF "An asynchronous web framework for C++ built on top of Qt")
 
 # Dependencies
-cmake_minimum_required(VERSION 3.1.0)
+cmake_minimum_required(VERSION 2.8.11)
 find_package(Qt5Core REQUIRED)
 find_package(Qt5Network REQUIRED)
 
+# CMake since 3.1 has ability to use particular C/C++ standarts.
+# For versions before 3.1 use FindCXX11 module as fallback.
+if("${CMAKE_VERSION}" VERSION_LESS "3.1")
+    set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake/modules" ${CMAKE_MODULE_PATH})
+    find_package(CXX11 REQUIRED)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CXX11_FLAGS}")
+endif()
+
 get_target_property(QMAKE_EXECUTABLE Qt5::qmake LOCATION)
 function(QUERY_QMAKE VAR RESULT)
     exec_program("${QMAKE_EXECUTABLE}" ARGS "-query ${VAR}" RETURN_VALUE return_code OUTPUT_VARIABLE output)

src/CMakeLists.txt

@@ -43,11 +43,19 @@ set_target_properties(
     VERSION ${TUFAO_VERSION}
     VS_KEYWORD Qt4VSv1.0
     AUTOMOC ON
-    CXX_STANDARD 11
-    CXX_STANDARD_REQUIRED ON
     INSTALL_NAME_DIR "${CMAKE_INSTALL_PREFIX}/${libdir}"
 )
 
+# CXX_STANDARD was introduced in CMake 3.1
+if("${CMAKE_VERSION}" VERSION_GREATER "3.0")
+    set_target_properties(
+        "${TUFAO_LIBRARY}"
+        PROPERTIES
+        CXX_STANDARD 11
+        CXX_STANDARD_REQUIRED ON
+    )
+endif()
+
 if("${CMAKE_VERSION}" VERSION_LESS "2.8.12")
   target_include_directories("${TUFAO_LIBRARY}" INTERFACE "${CMAKE_INSTALL_PREFIX}/${includedir}")
   install(TARGETS "${TUFAO_LIBRARY}" EXPORT "${TUFAO_LIBRARY}-export"

src/tests/CMakeLists.txt

@@ -25,9 +25,19 @@ macro(setup_test_target target)
         "${target}"
         PROPERTIES
         AUTOMOC ON
-        CXX_STANDARD 11
-        CXX_STANDARD_REQUIRED ON
     )
+
+    # CXX_STANDARD was introduced in CMake 3.1
+    if("${CMAKE_VERSION}" VERSION_GREATER "3.0")
+        set_target_properties(
+            "${target}"
+            PROPERTIES
+            CXX_STANDARD 11
+            CXX_STANDARD_REQUIRED ON
+        )
+endif()
+
+
     target_link_libraries("${target}" "${TUFAO_LIBRARY}")
 
     add_test(NAME "${target}"