UserspaceEmulator: Implement very basic leak checking :^)

Upon exit, the emulator will now print a leak report of any malloc
allocations that are still live and don't have pointers to their base
address anywhere in either another live mallocation, or in one of the
non-malloc-block memory regions.

Note that the malloc-block memory region check is not fully functional
and this will work even better once we get that fixed.

This is pretty cool. :^)

DevTools/UserspaceEmulator/SoftMMU.h

@@ -98,6 +98,8 @@ public:
 
     SharedBufferRegion* shbuf_region(int shbuf_id);
 
+    NonnullOwnPtrVector<Region>& regions() { return m_regions; }
+
 private:
     OwnPtr<Region> m_tls_region;
     NonnullOwnPtrVector<Region> m_regions;