Only send sigalgs extension in 1.2-capable ClientHellos.

BUG=https://code.google.com/p/webrtc/issues/detail?id=4223

Change-Id: I88eb036fdc6da17bc6a5179df02f35486abe9add
Reviewed-on: https://boringssl-review.googlesource.com/3030
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 64e8ea0..e26351b 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -913,7 +913,7 @@
     }
   }
 
-  if (SSL_USE_SIGALGS(s)) {
+  if (ssl3_version_from_wire(s, s->client_version) >= TLS1_2_VERSION) {
     size_t salglen;
     const uint8_t *salg;
     salglen = tls12_get_psigalgs(s, &salg);