fix check for CreateDefaultPlatform, fixes #313

Include libplatform.h, as meanwhile all supported V8 versions have that file.

config.m4

@@ -92,31 +92,22 @@ if test "$PHP_V8JS" != "no"; then
   AC_MSG_CHECKING([for libv8_libplatform])
   AC_DEFUN([V8_CHECK_LINK], [
     save_LIBS="$LIBS"
-	LIBS="$LIBS $1 -lv8_libplatform -lv8"
-	AC_LINK_IFELSE([AC_LANG_PROGRAM([
-	  namespace v8 {
-		namespace platform {
-		  enum class IdleTaskSupport { kDisabled, kEnabled };
-		  void* CreateDefaultPlatform($2);
-		}
-	  }
-	], [ v8::platform::CreateDefaultPlatform(); ])], [
-	  dnl libv8_libplatform.so found
-	  AC_MSG_RESULT(found)
-	  V8JS_SHARED_LIBADD="$1 -lv8_libplatform $V8JS_SHARED_LIBADD"
-      $3
-	], [ $4 ])
+    LIBS="$LIBS $1 -lv8_libplatform -lv8"
+    AC_LINK_IFELSE([AC_LANG_PROGRAM([
+      #include <libplatform/libplatform.h>
+    ], [ v8::platform::CreateDefaultPlatform(); ])], [
+      dnl libv8_libplatform.so found
+      AC_MSG_RESULT(found)
+      V8JS_SHARED_LIBADD="$1 -lv8_libplatform $V8JS_SHARED_LIBADD"
+        $3
+    ], [ $4 ])
     LIBS="$save_LIBS"
   ])
 
-  V8_CHECK_LINK([], [int thread_pool_size = 0, IdleTaskSupport idle_task_support = IdleTaskSupport::kDisabled], [], [
-    V8_CHECK_LINK([], [int thread_pool_size = 0], [], [
-      V8_CHECK_LINK([-lv8_libbase], [int thread_pool_size = 0, IdleTaskSupport idle_task_support = IdleTaskSupport::kDisabled], [], [
-        V8_CHECK_LINK([-lv8_libbase], [int thread_pool_size = 0], [], [
-          AC_MSG_ERROR([could not find libv8_libplatform library])
-        ])
-	  ])
-	])
+  V8_CHECK_LINK([], [], [], [
+    V8_CHECK_LINK([-lv8_libbase], [], [], [
+      AC_MSG_ERROR([could not find libv8_libplatform library])
+    ])
   ])