BUILD: ssl: silence a warning reported for ERR_remove_state()

In 1.0.0, this function was replaced with ERR_remove_thread_state().
As of openssl 1.1.0, both are now deprecated and do nothing at all.
Thus we simply make this call do nothing in 1.1.0 to silence the
warning.

The change was tested with 0.9.8, 1.0.0, 1.0.1, 1.0.2 and 1.1.0.

This kills the following warning on 1.1.0 :
   src/ssl_sock.c:7266:9: warning: 'ERR_remove_state' is deprecated (declared at /dev/shm/openssl-1.1.0b/include/openssl/err.h:247) [-Wdeprecated-declarations]

This fix should be backported to 1.7.
diff --git a/include/proto/openssl-compat.h b/include/proto/openssl-compat.h
index e2154f7..0194eaa 100644
--- a/include/proto/openssl-compat.h
+++ b/include/proto/openssl-compat.h
@@ -161,4 +161,14 @@
 }
 #endif
 
+/* ERR_remove_state() was deprecated in 1.0.0 in favor of
+ * ERR_remove_thread_state(), which was in turn deprecated in
+ * 1.1.0 and does nothing anymore. Let's simply silently kill
+ * it.
+ */
+#if (OPENSSL_VERSION_NUMBER >= 0x1010000fL)
+#undef  ERR_remove_state
+#define ERR_remove_state(x)
+#endif
+
 #endif /* _PROTO_OPENSSL_COMPAT_H */