Add allocation and garbage collection infrastructure.

Change-Id: I4b04cdfdf18afb75a7b0df87b509e8156b4a932b
diff --git a/src/globals.h b/src/globals.h
index 73afb7c..b2f73fd 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -12,9 +12,9 @@
 typedef intptr_t word;
 typedef uintptr_t uword;
 
-const int KB = 1024;
-const int MB = KB * KB;
-const int GB = KB * KB * KB;
+const size_t KB = 1024;
+const size_t MB = KB * KB;
+const size_t GB = KB * KB * KB;
 const int kMaxInt = 0x7FFFFFFF;
 const int kMinInt = -kMaxInt - 1;