Manual backport of https://github.com/RsyncProject/rsync/pull/867

--- a/access.c
+++ b/access.c
@@ -99,7 +99,7 @@ static void make_mask(char *mask, int pl
 	return;
 }
 
-static int match_address(const char *addr, const char *tok)
+static int match_address(const char *addr, char *tok)
 {
 	char *p;
 	struct addrinfo hints, *resa, *rest;
--- a/checksum.c
+++ b/checksum.c
@@ -176,7 +176,7 @@ void parse_checksum_choice(int final_cal
 	if (valid_checksums.negotiated_nni)
 		xfer_sum_nni = file_sum_nni = valid_checksums.negotiated_nni;
 	else {
-		char *cp = checksum_choice ? strchr(checksum_choice, ',') : NULL;
+		const char *cp = checksum_choice ? strchr(checksum_choice, ',') : NULL;
 		if (cp) {
 			xfer_sum_nni = parse_csum_name(checksum_choice, cp - checksum_choice);
 			file_sum_nni = parse_csum_name(cp+1, -1);
--- a/compat.c
+++ b/compat.c
@@ -131,7 +131,7 @@ static const char *client_info;
  * of that protocol for it to be advertised as available. */
 static void check_sub_protocol(void)
 {
-	char *dot;
+	const char *dot;
 	int their_protocol, their_sub;
 	int our_sub = get_subprotocol_version();
 
@@ -414,7 +414,7 @@ static const char *getenv_nstr(int ntype
 		env_str = ntype == NSTR_COMPRESS ? "zlib" : protocol_version >= 30 ? "md5" : "md4";
 
 	if (am_server && env_str) {
-		char *cp = strchr(env_str, '&');
+		const char *cp = strchr(env_str, '&');
 		if (cp)
 			env_str = cp + 1;
 	}
--- a/exclude.c
+++ b/exclude.c
@@ -904,7 +904,7 @@ static int rule_matches(const char *fnam
 {
 	int slash_handling, str_cnt = 0, anchored_match = 0;
 	int ret_match = ex->rflags & FILTRULE_NEGATE ? 0 : 1;
-	char *p, *pattern = ex->pattern;
+	const char *p, *pattern = ex->pattern;
 	const char *strings[16]; /* more than enough */
 	const char *name = fname + (*fname == '/');
 
--- a/io.c
+++ b/io.c
@@ -1159,7 +1159,7 @@ void set_io_timeout(int secs)
 static void check_for_d_option_error(const char *msg)
 {
 	static char rsync263_opts[] = "BCDHIKLPRSTWabceghlnopqrtuvxz";
-	char *colon;
+	const char *colon;
 	int saw_d = 0;
 
 	if (*msg != 'r'
--- a/loadparm.c
+++ b/loadparm.c
@@ -178,7 +178,7 @@ static char *expand_vars(const char *str
 
 	for (t = buf, f = str; bufsize && *f; ) {
 		if (*f == '%' && isUpper(f+1)) {
-			char *percent = strchr(f+1, '%');
+			const char *percent = strchr(f+1, '%');
 			if (percent && percent - f < bufsize) {
 				char *val;
 				strlcpy(t, f+1, percent - f);