options key parsing

OPTIONS=menu_previous_page:\mv
  BINDINGS=M-v:menu_previous_page
both worked, but
  OPTIONS=menu_previous_page:M-v
  BINDINGS=\mv:menu_previous_page
both failed.  Make all four variations work.  Tiny change made large
by the need to move some things around.

The option definition for menu_first_page had a couple of its flag
bits swapped.  I didn't try to figure out whether that had any impact.

include/global.h

@@ -443,4 +443,23 @@ struct savefile_info {
         (nhassert_failed(#expression, __FILE__, __LINE__), 0))
 #endif
 
+/* Macros for meta and ctrl modifiers:
+ *   M and C return the meta/ctrl code for the given character;
+ *     e.g., (C('c') is ctrl-c
+ */
+#ifndef M
+#ifndef NHSTDC
+#define M(c) (0x80 | (c))
+#else
+#define M(c) ((c) - 128)
+#endif /* NHSTDC */
+#endif
+
+#ifndef C
+#define C(c) (0x1f & (c))
+#endif
+
+#define unctrl(c) ((c) <= C('z') ? (0x60 | (c)) : (c))
+#define unmeta(c) (0x7f & (c))
+
 #endif /* GLOBAL_H */