Check for compiler flags not available with gcc < 4.
- https://github.com/lloyd/yajl/pull/256

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -12,7 +12,7 @@
 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 # OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-CMAKE_MINIMUM_REQUIRED(VERSION 2.6)
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8.0...3.10)
 
 PROJECT(YetAnotherJSONParser C)
 
@@ -54,9 +54,14 @@ ELSE (WIN32)
     IF(HAVE_GCC_VISIBILITY)
       SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden")
     ENDIF(HAVE_GCC_VISIBILITY)
+    CHECK_C_COMPILER_FLAG(-Wold-style-definition HAVE_GCC_WOLDSTYLE)
+    IF(HAVE_GCC_WOLDSTYLE)
+      SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wold-style-definition")
+    ENDIF(HAVE_GCC_WOLDSTYLE)
   ENDIF(CMAKE_COMPILER_IS_GNUCC)
   SET(CMAKE_C_FLAGS
-      "${CMAKE_C_FLAGS} -std=c99 -pedantic -Wpointer-arith -Wno-format-y2k -Wstrict-prototypes -Wmissing-declarations -Wnested-externs -Wextra	-Wundef -Wwrite-strings -Wold-style-definition -Wredundant-decls -Wno-unused-parameter -Wno-sign-compare -Wmissing-prototypes")
+      "${CMAKE_C_FLAGS} -std=c99 -pedantic -Wpointer-arith -Wno-format-y2k -Wstrict-prototypes -Wmissing-declarations -Wnested-externs -Wextra -Wundef -Wwrite-strings -Wredundant-decls -Wno-unused-parameter -Wno-sign-compare -Wmissing-prototypes")
+  
 
   SET(CMAKE_C_FLAGS_DEBUG "-DDEBUG -g")
   SET(CMAKE_C_FLAGS_RELEASE "-DNDEBUG -O2 -Wuninitialized")
