Added cast to qreal, avoiding ftbfs due to issue #758
More explanation here
https://wiki.debian.org/ArmEabiFixes
And on qt-project.org reference website:
"Typedef for double on all platforms except for those using CPUs with ARM architectures. On ARM-based platforms, qreal is a typedef for float for performance reasons."
Merge pull request #11 from LocutusOfBorg/fix-arm

Added cast to qreal, avoiding ftbfs due to issue #758