Cleanup/rearrange includes:
- factorize unistd.h and stdbool.h in lldb-types.h.
- Add <functional> and <string> where required.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@189477 91177308-0d34-0410-b5e6-96231b3b80d8