Garbage collect xobj->data.{ptr,pkey}

Garbage collect xobj->data.{ptr,pkey}

Both these are essentially unused. Remove the last use of data.ptr
by initializing and copying the X509_OBJECT using memset() and
struct assignment in X509_STORE_CTX_get_subject_by_name() and add
a missing error check for X509_OBJECT_up_ref_count() while there.

ok beck