tsan: fix and make faster GetRSS
It is currently broken because it reads a wrong value from profile (heap instead of total).
Also make it faster by reading /proc/self/statm. Reading of /proc/self/smaps
can consume more than 50% of time on beefy apps if done every 100ms.



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@213942 91177308-0d34-0410-b5e6-96231b3b80d8