Don't undef gettext, it breaks the build when it's disabled

Somewhere along the line, libintl.h is included whether or not
--disable-nls was passed to configure, and undefining gettext makes the
macros in that header make no sense.

src/bin/private.h

@@ -9,8 +9,6 @@
 #define _(string) gettext (string)
 #else
 #define _(string) (string)
-#undef gettext
-#define gettext(string) (string)
 #endif
 #define gettext_noop(String) String