Push an error on sigalg mismatch in X509_verify.

It was failing but not pushing an error. See
https://github.com/google/conscrypt/pull/537

Change-Id: Iafba1a5c0c7ef8e0535b335aa93df6f520c3803e
Reviewed-on: https://boringssl-review.googlesource.com/32044
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/x509.h b/include/openssl/x509.h
index 72f7314..ee3eccc 100644
--- a/include/openssl/x509.h
+++ b/include/openssl/x509.h
@@ -1200,5 +1200,6 @@
 #define X509_R_WRONG_TYPE 134
 #define X509_R_NAME_TOO_LONG 135
 #define X509_R_INVALID_PARAMETER 136
+#define X509_R_SIGNATURE_ALGORITHM_MISMATCH 137
 
 #endif