Move some typedefs to base.h.

Change-Id: I48bcf3a989752901903d68b50665910b9372a2ff
Reviewed-on: https://boringssl-review.googlesource.com/8860
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
diff --git a/include/openssl/x509v3.h b/include/openssl/x509v3.h
index fa78f33..67063bc 100644
--- a/include/openssl/x509v3.h
+++ b/include/openssl/x509v3.h
@@ -146,10 +146,10 @@
 
 typedef BIT_STRING_BITNAME ENUMERATED_NAMES;
 
-typedef struct BASIC_CONSTRAINTS_st {
+struct BASIC_CONSTRAINTS_st {
 int ca;
 ASN1_INTEGER *pathlen;
-} BASIC_CONSTRAINTS;
+};
 
 
 typedef struct PKEY_USAGE_PERIOD_st {