Filter out all symbols starting with a double underbar. In particular,

Filter out all symbols starting with a double underbar.  In particular,
this filters out all retguard symbols, which are no fun to guess. One
recognizes them easily but can get yourself hanged by a single digit!

An earlier version filtering only __retguard symbols was

ok deraadt, jsing

guenther agreed that filtering all double underbar symbols makes sense.
He also suggested to filter out symbols containing several consecutive
digits, but how much fun is guessing libcrypto symbols without all the
X509 goodness?