UserspaceEmulator: Start sketching out a SoftMMU class :^)

This Emulator sub-object will keep track of all active memory regions
and handle memory read/write operations from the CPU.

A memory region is currently represented by a virtual Region object
that can implement arbitrary behavior by overriding read/write ops.

DevTools/UserspaceEmulator/Emulator.h

@@ -27,6 +27,7 @@
 #pragma once
 
 #include "SoftCPU.h"
+#include "SoftMMU.h"
 #include <AK/Types.h>
 #include <LibX86/Instruction.h>
 #include <sys/types.h>
@@ -40,9 +41,14 @@ public:
     int exec(X86::SimpleInstructionStream&, u32 base);
     u32 virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3);
 
+    SoftMMU& mmu() { return m_mmu; }
+
 private:
+    SoftMMU m_mmu;
     SoftCPU m_cpu;
 
+    void setup_stack();
+
     uid_t virt$getuid();
     void virt$exit(int);