lib: obey to Misra rule 11.8 where possible

Casting away const-ness (or volatile-ness) is never a good idea, but
some library functions (e.g. strchr()) require doing so. Where not
required, remove / replace respective casts.

While there convert touched functions to Xen style.

No functional change intended.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>

xen/lib/memcpy.c

@@ -15,12 +15,13 @@
  */
 void *(memcpy)(void *dest, const void *src, size_t n)
 {
-	char *tmp = (char *) dest, *s = (char *) src;
+    char *tmp = dest;
+    const char *s = src;
 
-	while (n--)
-		*tmp++ = *s++;
+    while ( n-- )
+        *tmp++ = *s++;
 
-	return dest;
+    return dest;
 }
 
 /*

xen/lib/memmove.c

@@ -14,21 +14,25 @@
  */
 void *(memmove)(void *dest, const void *src, size_t n)
 {
-	char *tmp, *s;
+    char *tmp;
+    const char *s;
 
-	if (dest <= src) {
-		tmp = (char *) dest;
-		s = (char *) src;
-		while (n--)
-			*tmp++ = *s++;
-	} else {
-		tmp = (char *) dest + n;
-		s = (char *) src + n;
-		while (n--)
-			*--tmp = *--s;
-	}
+    if ( dest <= src )
+    {
+        tmp = dest;
+        s = src;
+        while ( n-- )
+            *tmp++ = *s++;
+    }
+    else
+    {
+        tmp = dest + n;
+        s = src + n;
+        while ( n-- )
+            *--tmp = *--s;
+    }
 
-	return dest;
+    return dest;
 }
 
 /*

xen/lib/strcmp.c

@@ -11,16 +11,15 @@
  */
 int (strcmp)(const char *cs, const char *ct)
 {
-	unsigned char *csu = (unsigned char *)cs;
-	unsigned char *ctu = (unsigned char *)ct;
-	int res;
+    const unsigned char *csu = (const void *)cs;
+    const unsigned char *ctu = (const void *)ct;
+    int res;
 
-	while (1) {
-		if ((res = *csu - *ctu++) != 0 || !*csu++)
-			break;
-	}
+    for ( ; ; )
+        if ( (res = *csu - *ctu++) != 0 || !*csu++ )
+            break;
 
-	return res;
+    return res;
 }
 
 /*

xen/lib/strncmp.c

@@ -12,17 +12,18 @@
  */
 int (strncmp)(const char *cs, const char *ct, size_t count)
 {
-	unsigned char *csu = (unsigned char *)cs;
-	unsigned char *ctu = (unsigned char *)ct;
-	int res = 0;
+    const unsigned char *csu = (const void *)cs;
+    const unsigned char *ctu = (const void *)ct;
+    int res = 0;
 
-	while (count) {
-		if ((res = *csu - *ctu++) != 0 || !*csu++)
-			break;
-		count--;
-	}
+    while ( count )
+    {
+        if ( (res = *csu - *ctu++) != 0 || !*csu++ )
+            break;
+        count--;
+    }
 
-	return res;
+    return res;
 }
 
 /*