Fix QHttp compilation on windows

external/qhttp/CMakeLists.txt

@@ -2,6 +2,8 @@ aux_source_directory(src HTTP_SRC)
 
 include_directories(src 3rdparty)
 
+add_definitions(-DQHTTP_EXPORT)
+
 set(CMAKE_AUTOMOC ON)
 add_library(qhttp STATIC ${HTTP_SRC} 3rdparty/http-parser/http_parser.c)
 target_link_libraries(qhttp)