Silence compiler warnings in browser example.

settings.cpp(138) : warning C4189: 'jar' : local variable is initialized but not  referenced
settings.cpp(240) : warning C4189: 'jar' : local variable is initialized but not referenced
searchlineedit.cpp: In member function 'virtual void ClearButton::paintEvent(QPaintEvent*)':
searchlineedit.cpp:68:12: warning: variable 'color' set but not used [-Wunused-but-set-variable]
networkaccessmanager.cpp: In member function 'void NetworkAccessManager::requestFinished(QNetworkReply*)':
networkaccessmanager.cpp:115:12: warning: unused variable 'pctCached' [-Wunused-variable]
networkaccessmanager.cpp:116:12: warning: unused variable 'pctPipelined' [-Wunused-variable]
networkaccessmanager.cpp:117:12: warning: unused variable 'pctSecure' [-Wunused-variable]
networkaccessmanager.cpp:118:12: warning: unused variable 'pctDownloadBuffer' [-Wunused-variable]
history.cpp: In member function 'virtual int HistoryMenuModel::rowCount(const QModelIndex&) const':
history.cpp:516:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
history.cpp: In member function 'virtual QModelIndex HistoryMenuModel::mapToSource(const QModelIndex&) const':
history.cpp:541:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

Change-Id: I76ba8ff28509f39c653e9b5ba707e380393dff0d
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>