scripts/emc.in: add DISPLAY_LD_PRELOAD, TASK_LD_PRELOAD workarounds
scripts/emc.in: add DISPLAY_LD_PRELOAD, TASK_LD_PRELOAD workarounds

if set, these variables will cause DISPLAY and TASK to be started as:

LD_PRELOAD=$TASK_LD_PRELOAD $EMCTASK ...
LD_PRELOAD=$DISPLAY_LD_PRELOAD $EMCDISPLAY...

reason: under certain conditions these commands might segfault on startup

see
http://stackoverflow.com/questions/2778193/segfault-during-cxa-allocate-exception-in-swig-wrapped-library
https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/259219
https://www.libavg.de/wiki/LinuxInstallIssues#glibc_invalid_pointer :

// this is actually a bug in libgl1-mesa-dri and it looks
// it has been fixed in mesa - 7.10.1-0ubuntu2

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