Provide a default constructor for TimeValue. This was used, but only in

if-ed out code paths and on Windows. Hopefully restores the Windows
build. Thanks to Reid Kleckner for helping triage this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171568 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/TimeValue.h

@@ -82,6 +82,9 @@ namespace sys {
   /// @name Constructors
   /// @{
   public:
+    /// \brief Default construct a time value, initializing to ZeroTime.
+    TimeValue() : seconds_(0), nanos_(0) {}
+
     /// Caller provides the exact value in seconds and nanoseconds. The
     /// \p nanos argument defaults to zero for convenience.
     /// @brief Explicit constructor