Remove TimeValue usage from llvm/Support

Remove TimeValue usage from llvm/Support

Summary:
This is a follow-up to D25416. It removes all usages of TimeValue from
llvm/Support library (except for the actual TimeValue declaration), and replaces
them with appropriate usages of std::chrono. To facilitate this, I have added
small utility functions for converting time points and durations into appropriate
OS-specific types (FILETIME, struct timespec, ...).

Reviewers: zturner, mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25730

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284966 91177308-0d34-0410-b5e6-96231b3b80d8