purge: Add a small command-line utility for purging all volatile memory

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/dfc5eb2b6d9

Userland/purge.cpp

@@ -0,0 +1,9 @@
+#include <stdio.h>
+#include <Kernel/Syscall.h>
+
+int main(int, char**)
+{
+    int purged_page_count = syscall(SC_purge);
+    printf("Purged page count: %d\n", purged_page_count);
+    return 0;
+}