PK: rename members for consistency CIPHER, MD

Also add pk_get_name() to remove a direct access to pk_type
diff --git a/library/x509parse.c b/library/x509parse.c
index 225f45d..e080174 100644
--- a/library/x509parse.c
+++ b/library/x509parse.c
@@ -2147,7 +2147,7 @@
     ret = x509parse_keyfile( &pk, path, pwd );
 
     if( ret == 0 )
-        rsa_copy( rsa, pk.data );
+        rsa_copy( rsa, pk_rsa( pk ) );
     else
         rsa_free( rsa );
 
@@ -2170,7 +2170,7 @@
     ret = x509parse_public_keyfile( &pk, path );
 
     if( ret == 0 )
-        rsa_copy( rsa, pk.data );
+        rsa_copy( rsa, pk_rsa( pk ) );
     else
         rsa_free( rsa );
 
@@ -2774,7 +2774,7 @@
     ret = x509parse_key( &pk, key, keylen, pwd, pwdlen );
 
     if( ret == 0 )
-        rsa_copy( rsa, pk.data );
+        rsa_copy( rsa, pk_rsa( pk ) );
     else
         rsa_free( rsa );
 
@@ -2798,7 +2798,7 @@
     ret = x509parse_public_key( &pk, key, keylen );
 
     if( ret == 0 )
-        rsa_copy( rsa, pk.data );
+        rsa_copy( rsa, pk_rsa( pk ) );
     else
         rsa_free( rsa );
 
@@ -3141,7 +3141,7 @@
     SAFE_SNPRINTF();
 
     if( ( ret = x509_key_size_helper( key_size_str, BEFORE_COLON,
-                                      crt->pk.info->name ) ) != 0 )
+                                      pk_get_name( &crt->pk ) ) ) != 0 )
     {
         return( ret );
     }