Implement issue #923: Make boost timer optional

Author: arvid-norlander

CMakeLists.txt

@@ -83,7 +83,7 @@ OPTION (MSGPACK_BUILD_EXAMPLES "Build msgpack examples." ON)
 
 SET (Boost_USE_MULTITHREADED      ON)
 SET (Boost_USE_STATIC_RUNTIME    OFF)
-FIND_PACKAGE (Boost REQUIRED COMPONENTS chrono system timer)
+FIND_PACKAGE (Boost REQUIRED COMPONENTS chrono system OPTIONAL_COMPONENTS timer)
 
 INCLUDE_DIRECTORIES (
    ${Boost_INCLUDE_DIRS}

example/cpp03/CMakeLists.txt

@@ -22,10 +22,12 @@ IF (NOT MSVC)
     )
 ENDIF ()
 
-LIST (APPEND with_boost_lib_PROGRAMS
-    speed_test.cpp
-    speed_test_nested_array.cpp
-)
+if (Boost_TIMER_LIBRARY)
+    LIST (APPEND with_boost_lib_PROGRAMS
+        speed_test.cpp
+        speed_test_nested_array.cpp
+    )
+endif()
 
 FOREACH (source_file ${exec_PROGRAMS})
     GET_FILENAME_COMPONENT (source_file_we ${source_file} NAME_WE)