Added support for building against Qt5

One can explicitly enable building against Qt5 by configuring QtTesting with
-DQtTesting_QT_VERSION:STRING="5". To specify custom Qt5 install paths, use
-DCMAKE_PREFIX_PATH:STRING=/home/sankhesh/Projects/qt5/qt5.2.0/5.2.0/gcc_64

Qt5 is built and packaged with the -reduce-relocations configure option as
default. This causes compilations to run with the -Bsymbolic-functions option,
which makes function pointer comparison ineffective, unless the -fPIE flag is
also supplied. Added Qt5 compile flags to support position independent code.
Qt5 obsoletes toAscii and fromAscii methods

Replaced all instances:
QString::toAscii --> QString::toLatin1
QString::fromAscii --> QString::fromLatin1
QChar::fromAscii --> QLatin1Char
QApplication::syncX() method has been removed in Qt5
Ignore Window objects when filtering events