Core/Threads: Include Helgrind suppressions file

Include a Helgrind suppressions file under source control. Each suppressed race is either a false positive, a read race followed by a lock acquire anyway, a bool race. Suppressions related to the same issue in the same function are grouped with a counter in brackets [ ] .

Fix tabs added in bcee801e4bdbf7d53f15cd0499e9d3aaedd3c3e2 .