Remove packed attribute from Rect

Fixes #3785 -- the issue where the Travis build failed because of gcc's
-Werror=address-of-packed-member.

Adds an equality function to avoid relying on memcmp().

include/util.h

@@ -64,6 +64,7 @@ int max(int a, int b);
 bool rect_contains(Rect rect, uint32_t x, uint32_t y);
 Rect rect_add(Rect a, Rect b);
 Rect rect_sub(Rect a, Rect b);
+bool rect_equals(Rect a, Rect b);
 
 /**
  * Returns true if the name consists of only digits.