A few changes in tests about number of bits in integers

- The preprocessor must work with at least 'long', and therefore must
do shifts of up to 31 bits correctly.
- Whenever possible, use unsigned types in shifts.

lutf8lib.c

@@ -28,7 +28,7 @@
 /*
 ** Integer type for decoded UTF-8 values; MAXUTF needs 31 bits.
 */
-#if ((UINT_MAX >> 15) >> 15) >= 1
+#if (UINT_MAX >> 30) >= 1
 typedef	unsigned int utfint;
 #else
 typedef unsigned long utfint;