[dfsan] Add custom function for pthread_create.

Differential Revision: http://llvm-reviews.chandlerc.com/D1504

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@189502 91177308-0d34-0410-b5e6-96231b3b80d8
[dfsan] Add custom function for dl_iterate_phdr.

Differential Revision: http://llvm-reviews.chandlerc.com/D1505

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@189503 91177308-0d34-0410-b5e6-96231b3b80d8