handy.h: Refactor FITS_IN_8_BITS()

By using a cast to U8, the '&' operation can be elminated, and the macro
easier to read.

handy.h

@@ -1438,10 +1438,10 @@ or casts
 #ifndef __COVERITY__
   /* The '| 0' part ensures a compiler error if c is not integer (like e.g., a
    * pointer) */
-#define FITS_IN_8_BITS(c) (   (sizeof(c) == 1)                      \
-                           || !(((WIDEST_UTYPE)((c) | 0)) & ~0xFF))
+#  define FITS_IN_8_BITS(c) (   (sizeof(c) == 1)                        \
+                             || ((WIDEST_UTYPE)((c) | 0) == ((U8)(c))))
 #else
-#define FITS_IN_8_BITS(c) (1)
+#  define FITS_IN_8_BITS(c) (1)
 #endif
 
 /* Returns true if l <= c <= (l + n), where 'l' and 'n' are non-negative