Add patch to install missing header.
It looks like version 4.2 is a bit messed up, as soap.h includes a
header which is not installed by default, breaking the build for ports
such as kdenetwork4.
Will report upstream at https://bugs.kde.org/285803.
Reported by: Jan Henrik Sylvester <email@example.com>
Approved by: avilla (mentor, implicit), Shane Bell <firstname.lastname@example.org>
Feature safe: yes