Declare arj_integrity_identifier as global.

Without this it's not added to resulting binary
and we need it.

--- src-orig/integr.c	2017-09-08 21:45:38.422802558 +0200
+++ src/integr.c	2017-09-08 22:25:22.853785365 +0200
@@ -5,7 +5,7 @@
  *
  */
 
-static volatile const char intergrity_identifier[] = {
+volatile const char arj_intergrity_identifier[] = {
 	0xB0, 0x03, 0xB0, 0x02, 0xB0, 0x03,
 	0xB0, 0x04, 0xB0, 0x05,
 	0x90, 0x90, 0x90, 0x90,