Implement parsing of OSC 8

Also start work on storing hyperlinks with cells

kitty/hyperlink.c

@@ -0,0 +1,28 @@
+/*
+ * hyperlink.c
+ * Copyright (C) 2020 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#define _POSIX_C_SOURCE 200809L
+#include <string.h>
+#include "screen.h"
+
+bool
+parse_osc_8(char *buf, char **id, char **url) {
+    char *boundary = strstr(buf, ";");
+    if (boundary == NULL) return false;
+    *boundary = 0;
+    if (*(boundary + 1)) *url = boundary + 1;
+    char *save, *token = strtok_r(buf, ":", &save);
+    while (token != NULL) {
+        size_t len = strlen(token);
+        if (len > 3 && token[0] == 'i' && token[1] == 'd' && token[2] == '=' && token[3]) {
+            *id = token + 3;
+            break;
+        }
+        token = strtok_r(NULL, ":", &save);
+    }
+    return true;
+}