Merge pull request microsoft#212 from denizt/ifndef

ifndef BOOST_ASIO_DISABLE_THREAD_KEYWORD_EXTENSION

Author: ras0219-msft

Release/include/cpprest/details/cpprest_compat.h

@@ -68,8 +68,10 @@
 // without this macro defined, it will create references to __tls_get_addr
 // which (while able to link) will not be available at runtime and prevent
 // the .so from loading.
+#if not defined BOOST_ASIO_DISABLE_THREAD_KEYWORD_EXTENSION
 #define BOOST_ASIO_DISABLE_THREAD_KEYWORD_EXTENSION
 #endif
+#endif
 
 #ifdef __clang__
 #include <cstdio>