Updated MD5 paths to grab the md5sums.txt file instead of a file with the same name as the binary installer. The md5sums.txt file contains all md5 checksums for the file in the same directory.
Updated tools.mk to grep in the md5 file for the row with the name of the file of interest.
Added makefile variables for the Qt version for easier upgrades in the future.
Updated the qt installer script to use Qt5.6
Removed Linux x32 installer since it is not provided anymore.
Fixed compiler errors caused by Qt5.6 using C++11 as default.
