some cmenu changes

cmenu/str.c

@@ -41,3 +41,17 @@ bool StringSub(String string, int start, int end, String *out_substr) {
 
 	return start_ok && end_ok;
 }
+
+String StringFromCString(unsigned char const *s) {
+	size_t size = 0;
+	while (s[size] != '\0') { size++; }
+	return (String) {
+		.buffer=s,
+		.size=size,
+	};
+}
+typedef struct String {
+	unsigned char const *buffer;
+	size_t size;
+} String;
+