Fix compilation with clang 3.4.

Note that I'm not too sure why this compiled with GCC
and why clang rejects the global operator== definition and
wants to have it in the KIO namespace. Someone with more C++
ADL knowledge should chime in whether this is the right fix.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from kio/tests/udsentrybenchmark.cpp:22:
In file included from /usr/include/qt/QtTest/QTest:1:
/usr/include/qt/QtTest/qtest.h:203:24:
error: call to function 'operator==' that is neither visible
in the template definition nor found by argument-dependent lookup

if (!(t1.at(i) == t2.at(i))) {
               ^

kio/tests/udsentrybenchmark.cpp:286:22: note: in instantiation of
function template specialization 'QTest::qCompare<KIO::UDSEntry>'
requested here

do { if (!QTest::qCompare(entries, m_smallEntries, "entries",

"m_smallEntries", "kio/tests/udsentrybenchmark.cpp", 286)) return;}
while (0);

kio/tests/udsentrybenchmark.cpp:246:6: note: 'operator==' should be
declared prior to the call site or in namespace 'KIO'

bool operator==(const KIO::UDSEntry &a, const KIO::UDSEntry &b)

^

1 error generated.
udsentrybenchmark.dir/build.make:54: recipe for target
'tests/CMakeFiles/udsentrybenchmark.dir/udsentrybenchmark.cpp.o'
failed
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

REVIEW: 116542