Get rid of sysctl includes on Linux.

The 'sysctl' syscall has been strongly deprecated on Linux for ages.
Currently, on old architectures it will spam syslog whenever used, and on
newer ones it's missing from the headers altogether.  Opencv has migrated
away on Linux already, but #includes were left lingering.  This commit
removes them on non-__APPLE__, unbreaking x32 (and probably others).

modules/core/src/parallel.cpp

@@ -56,7 +56,7 @@
     #include <sys/types.h>
     #if defined ANDROID
         #include <sys/sysconf.h>
-    #else
+    #elif defined __APPLE__
         #include <sys/sysctl.h>
     #endif
 #endif