More constness/C23 fixes [0.4.x]

src/diff.c

@@ -159,7 +159,7 @@ const char *stripped (const char *name, int num_components)
 
 unsigned long calculate_num_lines (const char *atatline, char which)
 {
-        char *p = strchr (atatline, which);
+        const char *p = strchr (atatline, which);
         if (!p)
                 return 1;
         while (*p && *p != ',' && *p != ' ') p++;
@@ -187,7 +187,7 @@ int read_atatline (const char *atatline,
 {
 	char *endptr;
 	unsigned long res;
-	char *p;
+	const char *p;
 
 	if (orig_offset) {
 		p = strchr (atatline, '-');

src/rediff.c

@@ -265,7 +265,7 @@ static void copy_to (struct hunk *from, struct hunk *upto,
 }
 
 /* Deal with an added hunk. */
-static long added_hunk (const char *meta, long offset, FILE *modify, FILE *t,
+static long added_hunk (char *meta, long offset, FILE *modify, FILE *t,
 			unsigned long morig_count, unsigned long mnew_count)
 {
 	long this_offset = 0;

src/util.c

@@ -250,7 +250,7 @@ FILE *xopen_seekable (const char *name, const char *mode)
 /* unzip if needed */
 FILE *xopen_unzip (const char *name, const char *mode)
 {
-	char *p, *zprog = NULL;
+	const char *p, *zprog = NULL;
 	FILE *fi, *fo;
 	const size_t buflen = 64 * 1024;
 	char *buffer;