Replace zones with individually tracked physical pages.

It's just a simple struct { ref_count, paddr }.
This will allow me to implement lazy zeroing and COW pages.

Userland/.gitignore

@@ -17,3 +17,4 @@ mm
 kill
 tty
 ft
+ft2

Userland/ft2.cpp

@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int main(int argc, char** argv)
+{
+    printf("Testing fork()...\n");
+    pid_t pid = fork();
+    if (!pid) {
+        printf("child, pid=%d\n", getpid());
+        for (;;);
+    } else {
+        printf("parent, child pid=%d\n", pid);
+        for (;;);
+    }
+    return 0;
+}