Fixed bug #924

Only use sysconf if _SC_NPROCESSORS_ONLN is available.  Fortunately the case for this was Mac OS X 10.4, which has sysctlbyname()

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%404356

src/cpuinfo/SDL_cpuinfo.c

@@ -308,7 +308,7 @@ int
 SDL_GetCPUCount()
 {
     if (!SDL_CPUCount) {
-#ifdef HAVE_SYSCONF
+#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
         if (SDL_CPUCount <= 0) {
             SDL_CPUCount = (int)sysconf(_SC_NPROCESSORS_ONLN);
         }