unicode.c: remove utf8_decode

unicode.c

@@ -13,41 +13,6 @@ size_t utf8_chsize(uint32_t ch) {
 	return 4;
 }
 
-static const uint8_t masks[] = {
-	0x7F,
-	0x1F,
-	0x0F,
-	0x07,
-	0x03,
-	0x01
-};
-
-uint32_t utf8_decode(const char **char_str) {
-	uint8_t **s = (uint8_t **)char_str;
-
-	uint32_t cp = 0;
-	if (**s < 128) {
-		// shortcut
-		cp = **s;
-		++*s;
-		return cp;
-	}
-	int size = utf8_size((char *)*s);
-	if (size == -1) {
-		++*s;
-		return UTF8_INVALID;
-	}
-	uint8_t mask = masks[size - 1];
-	cp = **s & mask;
-	++*s;
-	while (--size) {
-		cp <<= 6;
-		cp |= **s & 0x3f;
-		++*s;
-	}
-	return cp;
-}
-
 size_t utf8_encode(char *str, uint32_t ch) {
 	size_t len = 0;
 	uint8_t first;