Various cleanups.

* Remove disused macro.
* GCC doesn't seem to mind if IGNORE() is left off.
* Enumify phase codes.
* Use EXIT_* macros in all exit() calls.
* How did this even work without extern?
* Give advent.h a much-needed makeover.
* Use the chomp indicator in YAML string blocks to avoid code ugliness.

misc.c

@@ -242,11 +242,6 @@ void vspeak(const char* msg, va_list ap)
         }
     }
     *renderp = 0;
-
-    // Deal with messages that are in YAML block format and therefore
-    // have their own trailing \n
-    if (renderp > rendered && renderp[-1] == '\n')
-	*--renderp = '\0';
     
     // Print the message.
     printf("%s\n", rendered);