Add profiling infrastructure and widget

src/common/thread.h

@@ -24,6 +24,25 @@
 #include <unistd.h>
 #endif
 
+// Support for C++11's thread_local keyword was surprisingly spotty in compilers until very
+// recently. Fortunately, thread local variables have been well supported for compilers for a while,
+// but with semantics supporting only POD types, so we can use a few defines to get some amount of
+// backwards compat support.
+// WARNING: This only works correctly with POD types.
+#if defined(__clang__)
+#   if !__has_feature(cxx_thread_local)
+#       define thread_local __thread
+#   endif
+#elif defined(__GNUC__)
+#   if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8)
+#       define thread_local __thread
+#   endif
+#elif defined(_MSC_VER)
+#   if _MSC_VER < 1900
+#       define thread_local __declspec(thread)
+#   endif
+#endif
+
 namespace Common
 {