Add HIPPO module and starting tracking free physical pages

src/hulk/hulk.ld

@@ -26,9 +26,11 @@ SECTIONS
 
     .bss BLOCK(4K) : ALIGN(4K)
     {
+        _hulk_bss_start = .;
         *(COMMON)
         *(.bss)
     }
+    _hulk_bss_size = . - _hulk_bss_start;
 
     . = ALIGN(4K);