rsa/rsa_lib.c: const-ify RSA_get0_engine().

Reviewed-by: Rich Salz <rsalz@openssl.org>

crypto/rsa/rsa_lib.c

diff --git a/crypto/rsa/rsa_lib.c b/crypto/rsa/rsa_lib.c
index 14750d1..48e9100 100644
--- a/crypto/rsa/rsa_lib.c
+++ b/crypto/rsa/rsa_lib.c
@@ -304,7 +304,7 @@
     r->flags |= flags;
 }
 
-ENGINE *RSA_get0_engine(RSA *r)
+ENGINE *RSA_get0_engine(const RSA *r)
 {
     return r->engine;
 }

include/openssl/rsa.h

diff --git a/include/openssl/rsa.h b/include/openssl/rsa.h
index cd17385..b9d14e4 100644
--- a/include/openssl/rsa.h
+++ b/include/openssl/rsa.h
@@ -187,7 +187,7 @@
 void RSA_clear_flags(RSA *r, int flags);
 int RSA_test_flags(const RSA *r, int flags);
 void RSA_set_flags(RSA *r, int flags);
-ENGINE *RSA_get0_engine(RSA *r);
+ENGINE *RSA_get0_engine(const RSA *r);
 
 /* Deprecated version */
 DEPRECATEDIN_0_9_8(RSA *RSA_generate_key(int bits, unsigned long e, void