util: move string_is_safe() to string-util.[ch]

src/basic/string-util.c

@@ -765,3 +765,20 @@ char *string_free_erase(char *s) {
         string_erase(s);
         return mfree(s);
 }
+
+bool string_is_safe(const char *p) {
+        const char *t;
+
+        if (!p)
+                return false;
+
+        for (t = p; *t; t++) {
+                if (*t > 0 && *t < ' ') /* no control characters */
+                        return false;
+
+                if (strchr(QUOTES "\\\x7f", *t))
+                        return false;
+        }
+
+        return true;
+}