Fix various warnings when compiling with KRB5 code.

crypto/asn1/asn1.h

diff --git a/crypto/asn1/asn1.h b/crypto/asn1/asn1.h
index 170a2aa..dfd2244 100644
--- a/crypto/asn1/asn1.h
+++ b/crypto/asn1/asn1.h
@@ -440,6 +440,8 @@
 DECLARE_STACK_OF(ASN1_INTEGER)
 DECLARE_ASN1_SET_OF(ASN1_INTEGER)
 
+DECLARE_STACK_OF(ASN1_GENERALSTRING)
+
 typedef struct asn1_type_st
 	{
 	int type;