Fix broken polygonline and polygonitem for ARM.

Routes drawn on map became broken after pinch-zooming. Root cause was
inconsistent use of floating point types that only affects ARM
architecture. Fix is to switch double to qreal declarations.

I believe a more thorough review of the uses of doubles in QtLocation
needs to be done. See QTBUG-33331.

Change-Id: I72411d304d2e9183d415c2afdf0a31b80a4ad2a6
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>