net-im/psi: unbreak with libc++ 8

In file included from src/Certificates/moc_CertificateDisplayDialog.cpp:9:
In file included from src/Certificates/../../../psi-1.3/src/Certificates/CertificateDisplayDialog.h:23:
In file included from /usr/local/include/Qca-qt5/QtCrypto/QtCrypto:1:
In file included from /usr/local/include/Qca-qt5/QtCrypto/qca.h:36:
In file included from /usr/local/include/Qca-qt5/QtCrypto/qca_core.h:36:
In file included from /usr/local/include/qt5/QtCore/QString:1:
In file included from /usr/local/include/qt5/QtCore/qstring.h:48:
In file included from /usr/local/include/qt5/QtCore/qchar.h:43:
In file included from /usr/local/include/qt5/QtCore/qglobal.h:45:
In file included from /usr/include/c++/v1/type_traits:406:
In file included from /usr/include/c++/v1/cstddef:38:
version:1:1: error: expected unqualified-id
1.3
^

PR: 236192