tweaks: correct two conditions for conditional compilation

src/nano.h

@@ -164,7 +164,7 @@ typedef enum {
 #ifndef DISABLE_WRAPPING
     SPLIT_BEGIN, SPLIT_END,
 #endif
-#ifndef DISABLE_COMMENT
+#ifdef ENABLE_COMMENT
     COMMENT, UNCOMMENT, PREFLIGHT,
 #endif
     JOIN, PASTE, INSERT, ENTER, OTHER

src/proto.h

@@ -540,7 +540,7 @@ RETSIGTYPE cancel_command(int signal);
 bool execute_command(const char *command);
 void discard_until(const undo *thisitem, openfilestruct *thefile);
 void add_undo(undo_type action);
-#ifndef DISABLE_COMMENT
+#ifdef ENABLE_COMMENT
 void update_comment_undo(ssize_t lineno);
 #endif
 void update_undo(undo_type action);