Move X509_ALGOR to x509.h.

This matches OpenSSL and the name. Also accessors like X509_ALGOR_get0
are in x509.h.

Change-Id: Ic7583edcf04627cbfae822df11e75eebdd9ad7aa
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48770
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/x509.h b/include/openssl/x509.h
index 751117e..7768cc1 100644
--- a/include/openssl/x509.h
+++ b/include/openssl/x509.h
@@ -110,6 +110,13 @@
 #define X509v3_KU_DECIPHER_ONLY 0x8000
 #define X509v3_KU_UNDEF 0xffff
 
+struct X509_algor_st {
+  ASN1_OBJECT *algorithm;
+  ASN1_TYPE *parameter;
+} /* X509_ALGOR */;
+
+DECLARE_ASN1_FUNCTIONS(X509_ALGOR)
+
 DEFINE_STACK_OF(X509_ALGOR)
 
 typedef STACK_OF(X509_ALGOR) X509_ALGORS;