dungeon open failure

We've been getting numerous complaints from people
about "dungeon failure", often related to attempts
to start NetHack from within various zip utilities
that present a folder-like view.

The dungeon failure was actually misleading. The
real problem was a dlb file open failure, but the
return value of dlb_init() was not being checked
in pcmain.

This moves the dlb_init earlier in the startup,
checks for failure, and provides some feedback
around the common zip utility problem for win32.

doc/fixes35.0

@@ -203,6 +203,7 @@ some monsters can eat tins in addition to corpses to cure some ailments
 
 Platform- and/or Interface-Specific New Features
 ------------------------------------------------
+pcmain: check for dlb_init failure rather than relying on dungeon open failure
 win32gui: support perm_invent
 win32gui: menu option to add/remove windows captions
 win32gui: support for saving/restoring message history

sys/share/pcmain.c

@@ -6,6 +6,7 @@
 
 #include "hack.h"
 #include "dlb.h"
+#include "patchlevel.h"
 
 #ifndef NO_SIGNAL
 #include <signal.h>
@@ -271,6 +272,18 @@ char *argv[];
 	if (comp_times((long)time(&clock_time)))
 		error("Your clock is incorrectly set!");
 #endif
+	if (!dlb_init()) {
+	    pline("%s\n%s\n%s\n\nNetHack was unable to open the required file \"%s\".%s",
+		COPYRIGHT_BANNER_A, COPYRIGHT_BANNER_B,
+		COPYRIGHT_BANNER_C, DLBFILE,
+#ifdef WIN32
+			"\nAre you perhaps trying to run NetHack within a zip utility?");
+#else
+			"");
+#endif
+		error("dlb_init failure.");
+	}
+
 	u.uhp = 1;	/* prevent RIP on early quits */
 	u.ux = 0;	/* prevent flush_screen() */
 
@@ -397,8 +410,6 @@ char *argv[];
 	 */
 	vision_init();
 
-	dlb_init();
-
 	display_gamewindows();
 #ifdef WIN32
 	getreturn_enabled = TRUE;