Add DrWeb 4.31.3 support. Thanks to Wartan Hachaturow.

How-To-Repeat: 
diff -Nru avcheck.orig/files/patch-avcheck.c avcheck/files/patch-avcheck.c
--- avcheck.orig/files/patch-avcheck.c	Thu Jan  1 03:00:00 1970
+++ avcheck/files/patch-avcheck.c	Thu Mar 25 10:32:48 2004
@@ -0,0 +1,56 @@
+--- avcheck.c.orig	Sun Jul 28 00:22:05 2002
++++ avcheck.c	Thu Mar 25 10:32:17 2004
+@@ -530,23 +530,27 @@
+ #define DRWEBD_SCAN_FLAGS (DRWEBD_RETURN_VIRUSES/*|DRWEBD_HEURISTIC_ON*/)
+ 
+ /* DrWeb result codes */
+-#define DERR_READ_ERR		0x00001
+-#define DERR_WRITE_ERR		0x00002
+-#define DERR_NOMEMORY		0x00004
+-#define DERR_CRC_ERROR		0x00008
+-#define DERR_READSOCKET		0x00010
+-#define DERR_KNOWN_VIRUS	0x00020
+-#define DERR_UNKNOWN_VIRUS	0x00040
+-#define DERR_VIRUS_MODIFICATION	0x00080
+-#define DERR_TIMEOUT		0x00200
+-#define DERR_SYMLINK		0x00400
+-#define DERR_NO_REGFILE		0x00800
+-#define DERR_SKIPPED		0x01000
+-#define DERR_TOO_BIG		0x02000
+-#define DERR_TOO_COMPRESSED	0x04000
+-#define DERR_BAD_CALL		0x08000
+-#define DERR_EVAL_VERSION	0x10000
+-#define DERR_SPAM_MESSAGE	0x20000
++#define DERR_READ_ERR		0x00000001
++#define DERR_WRITE_ERR		0x00000002
++#define DERR_NOMEMORY		0x00000004
++#define DERR_CRC_ERROR		0x00000008
++#define DERR_READSOCKET		0x00000010
++#define DERR_KNOWN_VIRUS	0x00000020
++#define DERR_UNKNOWN_VIRUS	0x00000040
++#define DERR_VIRUS_MODIFICATION	0x00000080
++#define DERR_HAVE_CURED		0x00000100
++#define DERR_TIMEOUT		0x00000200
++#define DERR_SYMLINK		0x00000400
++#define DERR_NO_REGFILE		0x00000800
++#define DERR_SKIPPED		0x00001000
++#define DERR_TOO_BIG		0x00002000
++#define DERR_TOO_COMPRESSED	0x00004000
++#define DERR_BAD_CALL		0x00008000
++#define DERR_EVAL_VERSION	0x00010000
++#define DERR_SPAM_MESSAGE	0x00020000
++#define DERR_ARCHIVE_LEVEL      0x00040000
++#define DERR_HAVE_DELETED	0x00080000
++#define DERR_IS_CLEAN		0x00100000
+ 
+ #define DERR_VIRUS \
+   (DERR_KNOWN_VIRUS|DERR_UNKNOWN_VIRUS|DERR_VIRUS_MODIFICATION)
+@@ -570,7 +574,7 @@
+   if (read(fd, &c, sizeof(c)) != sizeof(c) || /* code */
+       read(fd, &n, sizeof(n)) != sizeof(n))   /* number of viruses */
+     err(errno, "error reading %s daemon response", avname);
+-  if ((c = ntohl(c)) == 0)
++  if (((c = ntohl(c)) == 0) || (c & DERR_IS_CLEAN))
+     return 0; /* all ok, no viruses found (n should be 0) */
+ 
+   if (!(c & DERR_VIRUS)) {