Get version-related functions from crypto.h rather than ssl.h.

(This makes it possible to include opensslv.h when not linking SSL.)

Change-Id: Id88c5ff44a7099d33d8d4672f7ba88986ffd1526
Reviewed-on: https://boringssl-review.googlesource.com/4831
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/opensslv.h b/include/openssl/opensslv.h
index 22f7e25..a3555d4 100644
--- a/include/openssl/opensslv.h
+++ b/include/openssl/opensslv.h
@@ -15,4 +15,4 @@
 /* This header is provided in order to make compiling against code that expects
    OpenSSL easier. */
 
-#include "ssl.h"
+#include "crypto.h"