Curses: add support for the palette config option

Depends on CHANGE_COLOR compile-time option.

Also allow multiple palette-definitions in the config file.

include/extern.h

@@ -327,6 +327,7 @@ extern boolean onlyhexdigits(const char *buf);
 extern uint32 get_nhcolor_from_256_index(int idx);
 #ifdef CHANGE_COLOR
 extern int count_alt_palette(void);
+extern int alternative_palette(char *);
 extern void change_palette(void);
 #endif