Removed code that conditionally included pthread.h for mingw.
This header is generally not available on mingw and can cause build errors.
The windows host code does provide timespec definition that can be used for
mingw case.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@203555 91177308-0d34-0410-b5e6-96231b3b80d8