Check for std::this_thread::sleep_for.

Summary:
- Some installations of libstdc++ don't have this defined. This happens
if they were built without --enable-libstdcxx-time. Detect this and
avoid tests that rely on this behavior.

Test Plan:
- fbconfig -r folly && fbmake runtests
- ./configure && make check on Ubuntu/FC/Mac

Reviewed By: meyering@fb.com

FB internal diff: D1002963

folly/configure.ac

@@ -78,6 +78,15 @@ AC_COMPILE_IFELSE(
    AC_DEFINE([OVERRIDE], [],
              [Define to "override" if the compiler supports C++11 "override"])]
 )
+
+AC_COMPILE_IFELSE(
+  [AC_LANG_SOURCE[
+    #include <thread>
+    #include <chrono>
+    void func() { std::this_thread::sleep_for(std::chrono::seconds(1)); }]],
+  [AC_DEFINE([HAVE_STD__THIS_THREAD__SLEEP_FOR], [1],
+             [Define to 1 if std::this_thread::sleep_for() is defined.])])
+
 AC_COMPILE_IFELSE(
   [AC_LANG_SOURCE[
     #include <type_traits>

folly/test/ThreadLocalTest.cpp

@@ -346,6 +346,7 @@ class FillObject {
 
 }  // namespace
 
+#if FOLLY_HAVE_STD__THIS_THREAD__SLEEP_FOR
 TEST(ThreadLocal, Stress) {
   constexpr size_t numFillObjects = 250;
   std::array<ThreadLocalPtr<FillObject>, numFillObjects> objects;
@@ -376,6 +377,7 @@ TEST(ThreadLocal, Stress) {
 
   EXPECT_EQ(numFillObjects * numThreads * numReps, gDestroyed);
 }
+#endif
 
 // Yes, threads and fork don't mix
 // (http://cppwisdom.quora.com/Why-threads-and-fork-dont-mix) but if you're