* grub-core/kern/misc.c (grub_strcmp): Use unsigned comparison as

per common usage and preffered in several parts of code.
	(grub_memcmp): Likewise.
	(grub_strncmp): Likewise.
	* include/grub/misc.h (grub_strcasecmp): Likewise.
	(grub_strncasecmp): Likewise.
	* Makefile.util.def (cmp_test): New test.
	(grub_script_strcmp): Likewise.
	* tests/cmp_unit_test.c: New file.
	* tests/grub_script_strcmp.in: Likewise.
	* grub-core/fs/hfsplus.c (grub_hfsplus_cmp_catkey): Add a comment.

grub-core/fs/hfsplus.c

@@ -532,6 +532,8 @@ grub_hfsplus_cmp_catkey (struct grub_hfsplus_key *keya,
   len = grub_be_to_cpu16 (catkey_a->namelen);
   if (len > catkey_b->namelen)
     len = catkey_b->namelen;
+  /* Since it's big-endian memcmp gives the same result as manually comparing
+     uint16_t but may be faster.  */
   diff = grub_memcmp (catkey_a->name, catkey_b->name,
 		      len * sizeof (catkey_a->name[0]));
   if (diff == 0)

grub-core/kern/misc.c

@@ -216,8 +216,8 @@ grub_vprintf (const char *fmt, va_list args)
 int
 grub_memcmp (const void *s1, const void *s2, grub_size_t n)
 {
-  const char *t1 = s1;
-  const char *t2 = s2;
+  const grub_uint8_t *t1 = s1;
+  const grub_uint8_t *t2 = s2;
 
   while (n--)
     {
@@ -252,7 +252,7 @@ grub_strcmp (const char *s1, const char *s2)
       s2++;
     }
 
-  return (int) *s1 - (int) *s2;
+  return (int) (grub_uint8_t) *s1 - (int) (grub_uint8_t) *s2;
 }
 
 int
@@ -270,7 +270,7 @@ grub_strncmp (const char *s1, const char *s2, grub_size_t n)
       s2++;
     }
 
-  return (int) *s1 - (int) *s2;
+  return (int) (grub_uint8_t) *s1 - (int) (grub_uint8_t)  *s2;
 }
 
 char *