Include thread.h from crypto.h, like OpenSSL.

thread.h defines |CRYPTO_num_locks| and friends.

Change-Id: Id28484d20226bf3ab49b2a75c48210167b96a2f3
Reviewed-on: https://boringssl-review.googlesource.com/5592
Reviewed-by: Adam Langley <agl@google.com>

include/openssl/crypto.h

@@ -21,6 +21,10 @@
  * mem.h. */
 #include <openssl/mem.h>
 
+/* Upstream OpenSSL defines |CRYPTO_LOCK|, etc., in crypto.h rather than
+ * thread.h. */
+#include <openssl/thread.h>
+
 
 #if defined(__cplusplus)
 extern "C" {