{
   PoclReleaseEvent_1
   Helgrind:Race
   ...
   fun:POclReleaseEvent
   ...
   fun:start_thread
   fun:clone
}
{
   DubiousLock
   Helgrind:Misc
   ...
   fun:__pthread_cond_wait_common
   ...
   fun:pthread_scheduler_get_work
   fun:pocl_pthread_driver_thread
   ...
   fun:start_thread
   fun:clone
}

Add file with helgrind suppressions
Add file with helgrind suppressions

This has suppressions for two reported issues.

One is a race in clReleaseEvent which should never occur
(unless someone calls a cl* API on a freed cl_event),
the other is a supposed lock problem but i don't yet
see how it could happen.

Tested with math_brute_force from OpenCL-CTS which uses
multiple threads to submit OpenCL work, except these two
there are no more helgrind issues from libpocl.
