qreal is a Qt typedef that used to be defined as float on ARM and
double on all other platforms.
However, since Qt 5.2 release candidate 1, qreal is double everywhere
(in Debian we are considering to keep it double on armel, but that
isn't relevant to Ubuntu). Please be prepared to update your packages
if they rely on the old behaviour.
We will probably need to do a transition (i.e. rebuild everything
that has armhf binaries), however the problem is that upstream did
not bump the SONAME of Qt libraries, so we are considering doing the
bump as a Debian/Ubuntu-specific change.
Feel free to express your opinion about (not) bumping the SONAME at
http://bugs.debian.org/731261 (that bug also contains links to
previous discussions on this subject).