增加一些注释

librf/src/event.h

 		};
 	}
 
+	//提供一种在协程和非协程之间同步的手段。
+	//典型用法是在非协程的线程，或者异步代码里，调用signal()方法触发信号，
+	//协程代码里，调用co_await wait()等系列方法等待同步。
 	struct event_t
 	{
 		typedef std::shared_ptr<detail::event_impl> event_impl_ptr;

tutorial/test_async_event.cpp

 
 using namespace resumef;
 
+//非协程的逻辑线程，或异步代码，可以通过event_t通知到协程，并且不会阻塞协程所在的线程。
 std::thread async_set_event(const event_t & e, std::chrono::milliseconds dt)
 {
 	return std::thread([=]

tutorial/test_async_resumable.cpp

 	std::cout << idx << ":" << name << "    ";
 	std::cout << N << "      " << ns << " ns      ";
 	std::cout << (ns / N) << " ns/op" << "    ";
-	std::cout << (N * 100 * 1000 / ns) << "w/cps" << std::endl;
+	std::cout << (N * 100ll * 1000ll / ns) << "w/cps" << std::endl;
 
 	lock_console.unlock();
 }

vs_proj/librf.cpp

 extern void resumable_main_benchmark_asio_server();
 extern void resumable_main_benchmark_asio_client(intptr_t nNum);
 
-int main(int argc, const char * argv[])
+int main(int argc, const char* argv[])
 {
 	resumable_main_modern_cb();
 	//resumable_main_benchmark_mem();

vs_proj/librf.vcxproj

     <ProjectGuid>{C1D4A6BD-592F-4E48-8178-7C87219BF80E}</ProjectGuid>
     <Keyword>Win32Proj</Keyword>
     <RootNamespace>librf</RootNamespace>
-    <WindowsTargetPlatformVersion>10.0.17763.0</WindowsTargetPlatformVersion>
+    <WindowsTargetPlatformVersion>10.0</WindowsTargetPlatformVersion>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>true</UseDebugLibraries>
-    <PlatformToolset>v141</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <CharacterSet>NotSet</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>false</UseDebugLibraries>
-    <PlatformToolset>v140</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <WholeProgramOptimization>true</WholeProgramOptimization>
     <CharacterSet>NotSet</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>true</UseDebugLibraries>
-    <PlatformToolset>v141</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <CharacterSet>NotSet</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>false</UseDebugLibraries>
-    <PlatformToolset>v140</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <WholeProgramOptimization>true</WholeProgramOptimization>
     <CharacterSet>NotSet</CharacterSet>
   </PropertyGroup>
     <ClCompile Include="..\tutorial\test_async_timer.cpp" />
     <ClCompile Include="..\tutorial\test_async_when_all.cpp" />
     <ClCompile Include="..\tutorial\test_async_yield_return.cpp" />
-    <ClCompile Include="librf.cpp" />
+    <ClCompile Include="librf.cpp">
+      <BasicRuntimeChecks Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Default</BasicRuntimeChecks>
+      <BufferSecurityCheck Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">false</BufferSecurityCheck>
+      <SDLCheck Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">false</SDLCheck>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\librf\librf.h" />