updated error suppression for newer versions of Qt

this new suppression file was tested with Qt 4.8.2, 4.8.4 and 4.8.6 with
valgrind 3.7.0 (Mint 13/Ubuntu 12.04 default) and valgrind 3.9.0
(installed from source code); the previous suppression file only worked
with Qt 4.8.2 and maybe earlier but not with 4.8.4 and 4.8.6 (other
versions not tested)