Description: Fix FTBFS with gcc-10

---

--- libsieve-2.2.6.orig/src/sv_parser/addr.c
+++ libsieve-2.2.6/src/sv_parser/addr.c
@@ -144,7 +144,7 @@ OF OR IN CONNECTION WITH THE USE OR PERF
 
 /* There are global to this file */
 char *libsieve_addrptr;          /* pointer to sieve string for address lexer */
-struct sieve2_context *libsieve_parse_context;
+extern struct sieve2_context *libsieve_parse_context;
 static struct address *addr = NULL;
 static struct mlbuf *ml = NULL;