Several changes and updates: (1) Added a new keyword "required" to the

tech file format "version" section.  This can be used to specify the
version of magic that must be used to be compatible with the tech file.
This effectively supercedes the technology version number.  (2) Changed
the behavior of "make" to set the version and revision numbers on doing
"make" instead of "configure".  This allows the version to update
correctly after doing a "git pull" followed by "make" without doing
"configure" in between.  (3) Fixed a couple of issues that were flagged
as compile-time warnings.

database/DBtech.c

@@ -204,9 +204,57 @@ DBTechSetVersion(sectionName, argc, argv)
 	}
 	return TRUE;
     }
+    if (strcmp(argv[0], "requires") == 0)
+    {
+	/* Version requirement check.  If the techfile has "requires" followed
+	 * by a magic version number in the form [magic-]<major>.<minor>.<revision>,
+	 * then the version of magic is checked against this, and the tech
+	 * loading will fail if there is a version incompatibility.
+	 */
+
+	int major, minor, rev;
+	int rmajor, rminor, rrev;
+	bool goodversion = FALSE;
+	char *vstring;
+
+	vstring = argv[1];
+	while ((*vstring != '\0') && !isdigit(*vstring)) vstring++;
+
+	major = minor = rev = 0;
+	rmajor = rminor = rrev = 0;
+	
+	if (sscanf(vstring, "%d.%d.%d", &rmajor, &rminor, &rrev) == 0)
+	{
+	    TechError("Badly formed magic version string, should be major.minor.rev\n");
+	    return FALSE;
+	}
+	sscanf(MagicVersion, "%d.%d", &major, &minor);
+	sscanf(MagicRevision, "%d", &rev);
+	if (major > rmajor)
+	    goodversion = TRUE;
+	else if (major == rmajor)
+	{
+	    if (minor > rminor)
+		goodversion = TRUE;
+	    else if (minor == rminor)
+	    {
+		if (rev >= rrev)
+		    goodversion = TRUE;
+	    }
+	}
+	if (goodversion == FALSE)
+	{
+	    TechError("Error:  Magic version %d.%d.%d is required by this "
+		    "techfile, but this version of magic is %d.%d.%d.\n",
+		    rmajor, rminor, rrev, major, minor, rev);
+	    return FALSE;
+	}
+	return TRUE;
+    }
 
 usage:
-    TechError("Badly formed version line\nUsage: {version text}|{description text}\n");
+    TechError("Badly formed version line\n"
+	    "Usage: {version text}|{description text}|{requires text}\n");
     return FALSE;
 }