Clang: Compile fix for Qt 4

pchmanager.cpp:325:21: error: 'CppTools::ProjectPart::Ptr' has no member
named 'reset' projectPart.reset();

clangcompletion_test.cpp:305:59: error: no viable conversion from
'QLatin1Char' to 'const QString'
	.arg(text).arg(texts.join(QLatin1Char(','))));

Task-Number: QTCREATORBUG-12122
Change-Id: Ie591594da1e3d357e38efe216d758f15ad6c2cd2
Reviewed-by: Eike Ziller <eike.ziller@digia.com>