Fix Qt version check in configure script
Fix Qt version check in configure script

The existing script uses awk to convert the version number to a float,
then compares that to 5.6.  I have Qt 5.11 installed; numerically,
5.11 < 5.6, so it thinks I have an old version of Qt.  Fix this by
splitting by "." and comparing the version components individually.

j-b-m/mlt,mltframework/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt