remove time_t from struct you (trunk only)

There was an issue reported where save files between different
versions of a manufacturer's compiler were incompatible because the time_t
ubirthday field was changed from 32 bits to 64 bits.

32 bit time_t implementations will break at 19:14:07 on  January 18, 2038.
64 bit time_t implementations will break at 23:59:59 on December 31, 3000.

This removes the dependency on the size of time_t from the save file.
The ubirthday field is no longer embedded in struct you.
This also adds two general purpose routines to hacklib.c, one to convert a time
value to a 14 character char representation and the other to convert that
back to time_t. Those are used by the save/restore routines.

This is a savefile breaking change, so editlevel in patchlevel.h was
incremented.

include/decl.h

@@ -251,6 +251,7 @@ E NEARDATA anything zeroany;		/* init'd and defined in decl.c */
 
 #include "you.h"
 E NEARDATA struct you u;
+E NEARDATA time_t ubirthday;
 
 #include "onames.h"
 #ifndef PM_H		/* (pm.h has already been included via youprop.h) */

include/extern.h

@@ -850,6 +850,8 @@ E char *FDECL(yymmdd, (time_t));
 #endif
 E long FDECL(yyyymmdd, (time_t));
 E long FDECL(hhmmss, (time_t));
+E char *FDECL(yyyymmddhhmmss,(time_t));
+E time_t FDECL(time_from_yyyymmddhhmmss, (char *));
 E int NDECL(phase_of_the_moon);
 E boolean NDECL(friday_13th);
 E int NDECL(night);

include/patchlevel.h

@@ -13,7 +13,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL	39
+#define EDITLEVEL	40
 
 #define COPYRIGHT_BANNER_A \
 "NetHack, Copyright 1985-2007"

include/you.h

@@ -355,8 +355,6 @@ struct you {
 #endif
 	int	umortality;		/* how many times you died */
 	int ugrave_arise; /* you die and become something aside from a ghost */
-	time_t	ubirthday;		/* real world time when game began */
-
 	int	weapon_slots;		/* unused skill slots */
 	int	skills_advanced;		/* # of advances made so far */
 	xchar	skill_record[P_SKILL_LIMIT];	/* skill advancements */