memory testing: resolved issues with newer lts release

the latest lts release of mint/ubuntu (17/14.04) contains newer version
ld-2.19.so library (a library containing the low-level memory allocation
functions), which causes valgrind to report memory issues differently
than with the older version (ld-2.15.so)

the cmake build file was modified to detect ld-2.19.so (32-bit or
64-bit) and if present, copies a different error suppression file to the
binary directory; this error suppression file is independent to the
version of Qt and so does not actually need configuring