Allowing multiple inputs when --non-inter mode is specified

[Nikos Mavrogiannopoulos]

Hello,
 There was an openwrt user which needed to supply a fixed second
password, but that's not possible currently when --non-inter is
specified. His use case was a mobile phone-based authentication, when a
specific keyword was used in 2FA. You can see more information in [0].

My solution to that problem was the following patch. That allows reading
multiple lines from stdin when --passwd-on-stdin is given, and that
input will be provided to the forms.
https://github.com/nmav/openconnect-mine/commit/7ab5ad2ab3e636540fef9134b9cd00a353365a62

regards,
Nikos

[0]. https://github.com/openwrt/packages/issues/1419