MEDIUM: shctx: allow the use of multiple shctx

Add an shctx argument which permits to create new independent shctx
area.
diff --git a/include/types/shctx.h b/include/types/shctx.h
index 9c384d9..6ab6460 100644
--- a/include/types/shctx.h
+++ b/include/types/shctx.h
@@ -46,6 +46,6 @@
 	struct shared_block free;
 };
 
-extern struct shared_context *shctx;
+extern struct shared_context *ssl_shctx;
 
 #endif