net-im/centerim{,-devel}: Fix build with Clang 6

In file included from rsshook.cc:32:
../../src/icqface.h:248:50: error: cannot combine with previous 'bool' declaration specifier

bool findresults(const imsearchparams &sp, bool auto = false);
                                                ^

... and more if one gets past this

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p479076_s338486/logs/errors/centerim-4.22.10_5.log
http://beefy12.nyi.freebsd.org/data/head-amd64-default/p479076_s338486/logs/errors/centerim-devel-4.22.10.11_7.log

PR: 230904
Approved by: frank@altpeter.de (maintainer timeout, 2 weeks)