FEAT: enhanced DEHEX with /escape refinement for changing the escape character

Can be used as:
```
>> dehex/escape "a#20b" #"#"
== "a b"
```

Author: Oldes

src/boot/natives.r

@@ -531,6 +531,7 @@ uppercase: native [
 dehex: native [
 	{Converts URL-style hex encoded (%xx) strings. If input is UTF-8 encode, you should first convert it to binary!}
 	value [any-string! binary!] {The string to dehex}
+	/escape char [char!] {Can be used to change the default escape char #"%"}
 ]
 
 enhex: native [

src/core/n-strings.c

@@ -560,17 +560,21 @@ static struct digest {
 **
 ***********************************************************************/
 {
-	REBVAL *arg = D_ARG(1);
+	REBVAL *arg        = D_ARG(1);
+//	REBOOL  ref_escape = D_REF(2);
+	REBVAL *val_escape = D_ARG(3);
 	REBINT len = (REBINT)VAL_LEN(arg); // due to len -= 2 below
 	REBUNI n;
 	REBSER *ser;
 
+	const REBCHR escape_char = (IS_CHAR(val_escape)) ? VAL_CHAR(val_escape) : '%';
+
 	if (VAL_BYTE_SIZE(arg)) {
 		REBYTE *bp = VAL_BIN_DATA(arg);
 		REBYTE *dp = Reset_Buffer(BUF_FORM, len);
 
 		for (; len > 0; len--) {
-			if (*bp == '%' && len > 2 && Scan_Hex2(bp+1, &n, FALSE)) {
+			if (*bp == escape_char && len > 2 && Scan_Hex2(bp+1, &n, FALSE)) {
 				*dp++ = (REBYTE)n;
 				bp += 3;
 				len -= 2;
@@ -586,7 +590,7 @@ static struct digest {
 		REBUNI *dp = (REBUNI*)Reset_Buffer(BUF_MOLD, len);
 
 		for (; len > 0; len--) {
-			if (*up == '%' && len > 2 && Scan_Hex2((REBYTE*)(up+1), &n, TRUE)) {
+			if (*up == escape_char && len > 2 && Scan_Hex2((REBYTE*)(up+1), &n, TRUE)) {
 				*dp++ = (REBUNI)n;
 				up += 3;
 				len -= 2;

src/tests/units/series-test.r3

@@ -644,6 +644,10 @@ Rebol [
 	--assert "%C2%81" = enhex to-string #{81}
 	--assert "%E5%85%83" = enhex {元}
 
+--test-- "DEHEX/escape"
+	--assert "C# #XX" = dehex/escape "C#23#20#XX" #"#"
+	--assert "(š)"    = dehex/escape "#28š#29"    #"#"
+
 
 ===end-group===