make exports more consistent (#511)

Author: DmitriyMusatkin

include/aws/http/exports.h

@@ -6,7 +6,7 @@
  * SPDX-License-Identifier: Apache-2.0.
  */
 
-#if defined(USE_WINDOWS_DLL_SEMANTICS) || defined(WIN32)
+#if defined(AWS_CRT_USE_WINDOWS_DLL_SEMANTICS) || defined(_WIN32)
 #    ifdef AWS_HTTP_USE_IMPORT_EXPORT
 #        ifdef AWS_HTTP_EXPORTS
 #            define AWS_HTTP_API __declspec(dllexport)
@@ -18,12 +18,12 @@
 #    endif /* USE_IMPORT_EXPORT */
 
 #else
-#    if ((__GNUC__ >= 4) || defined(__clang__)) && defined(AWS_HTTP_USE_IMPORT_EXPORT) && defined(AWS_HTTP_EXPORTS)
+#    if defined(AWS_HTTP_USE_IMPORT_EXPORT) && defined(AWS_HTTP_EXPORTS)
 #        define AWS_HTTP_API __attribute__((visibility("default")))
 #    else
 #        define AWS_HTTP_API
-#    endif /* __GNUC__ >= 4 || defined(__clang__) */
+#    endif
 
-#endif /* defined(USE_WINDOWS_DLL_SEMANTICS) || defined(WIN32) */
+#endif /* defined(AWS_CRT_USE_WINDOWS_DLL_SEMANTICS) || defined(_WIN32) */
 
 #endif /* AWS_HTTP_EXPORTS_H */