Begin work on separating int and word sizes (i.e. size_of(int) might not equal size_of(uintptr))

core/runtime/core.odin

@@ -425,7 +425,7 @@ Raw_Map :: struct {
 	// Map_Hash directly, though for consistency sake it's written as if it were
 	// an array of Map_Cell(Map_Hash).
 	data:      uintptr,   // 8-bytes on 64-bits, 4-bytes on 32-bits
-	len:       int,       // 8-bytes on 64-bits, 4-bytes on 32-bits
+	len:       uintptr,   // 8-bytes on 64-bits, 4-bytes on 32-bits
 	allocator: Allocator, // 16-bytes on 64-bits, 8-bytes on 32-bits
 }