Ensure use of __thread keyword is disabled for older Intel compilers.

asio/include/asio/detail/config.hpp

diff --git a/asio/include/asio/detail/config.hpp b/asio/include/asio/detail/config.hpp
index 28a1b57..f990f07 100644
--- a/asio/include/asio/detail/config.hpp
+++ b/asio/include/asio/detail/config.hpp
@@ -376,7 +376,11 @@
 # if defined(__linux__)
 #  if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
 #   if ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 3)) || (__GNUC__ > 3)
-#    define ASIO_HAS_THREAD_KEYWORD_EXTENSION 1
+#    if !defined(__INTEL_COMPILER) && !defined(__ICL)
+#     define ASIO_HAS_THREAD_KEYWORD_EXTENSION 1
+#    elif defined(__INTEL_COMPILER) && (__INTEL_COMPILER >= 1200)
+#     define ASIO_HAS_THREAD_KEYWORD_EXTENSION 1
+#    endif // defined(__INTEL_COMPILER) && (__INTEL_COMPILER >= 1200)
 #   endif // ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 3)) || (__GNUC__ > 3)
 #  endif // defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
 # endif // defined(__linux__)