fn_escape: Do not use unicode regex

The approach with glib regex is wrong here, because the pattrern works
on unicode characters not on bytes. So we might match a multi-byte
character.

Do it manually and escape every byte which is not a ascii graph
character.

cmirror.c

@@ -23,6 +23,7 @@
 #include <sys/utsname.h>
 #include <utime.h>
 #include <sys/time.h>
+#include <ctype.h>
 
 // https://www.manpagez.com/html/glib/glib-2.56.0/glib-Double-ended-Queues.php
 // http://owww.molgen.mpg.de/~buczek/glib-doc/
@@ -82,25 +83,15 @@ static char **match_re(GRegex *regex, char *string) {
     match_re(regex, string);         \
 })
 
-static gboolean fn_escape_cb(const GMatchInfo *match_info, GString *result,  gpointer user_data) {
-    (void)user_data;
-    g_autofree char *c = g_match_info_fetch(match_info, 0);
-    assert(c && c[0] != '\0' && c[1] == '\0');
-    g_string_append_printf(result, "\\x%02x", *c);
-    return FALSE;
-}
-
 static char *fn_escape(char *fn) {
-    static GRegex *regex = NULL;
-    if (!regex) {
-        regex = compile_pattern("([[:^graph:]\\\\])");
+    GString *out = g_string_sized_new(80);
+    for (char c = *fn++ ; c ; c = *fn++) {
+        if (isgraph(c))
+            g_string_append_c(out, c);
+        else
+            g_string_append_printf(out, "\\x%02x", (unsigned char)c);
     }
-    GError *error;
-
-    char *ret = g_regex_replace_eval(regex, fn, -1, 0, 0, fn_escape_cb, NULL, &error);
-    if (!ret)
-        die("%s\n", error->message);
-    return ret;
+    return g_string_free(out, FALSE);
 }
 
 static gboolean fn_unescape_cb(const GMatchInfo *match_info, GString *result,  gpointer user_data) {