Header consolidation - main.h, misc.h, and share.h merge to advent.h.

For a project this small size with a small type ontology, it's better
C style to have one header where all the assumptions about types and
structures are immediately visible.

This is a first step towards turning all that global state into a handful
of structures - probably just two, one saveable as a binary game state.

main.c

@@ -9,9 +9,8 @@
 #include <getopt.h>
 #include <signal.h>
 #include <time.h>
-#include "main.h"
+#include "advent.h"
 #include "database.h"
-#include "misc.h"
 
 long ABB[186], ATLOC[186], BLKLIN = true, DFLAG,
 		DLOC[7], FIXED[101], HOLDNG,