double declaration of bool false and true (conflicting with stdbool.h)

[Patrick Winnertz <winnie@…>]

Hey,
There is already a definition of bool in C, which uses also false and true,
therefore mc fails to build with ncurses currently as ncurses include
stdbool.h> where these are defined:

#ifndef _STDBOOL_H
#define _STDBOOL_H

#ifndef cplusplus

#define bool _Bool
#define true 1
#define false 0

#else /* cplusplus */
.....
#endif

So we should remove this completly from mhl/* and use this instead.