Fix definition of kdq_*_t for non-64-bit platforms

Author: dpward

kdq.h

@@ -3,10 +3,11 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <limits.h>
 
 #define __KDQ_TYPE(type) \
 	typedef struct { \
-		size_t front:58, bits:6, count, mask; \
+		size_t front:((CHAR_BIT * sizeof(size_t)) - 6), bits:6, count, mask; \
 		type *a; \
 	} kdq_##type##_t;