add link to legacy branch; update openssl version.

doc/Build-on-Windows.md

@@ -2,16 +2,16 @@
 
 I'm using [Visual Studio 2019 Community](https://visualstudio.microsoft.com/vs/community/), but I think 2017 should be OK, too.
 
-Webcc depends on `std::filesystem` which is a C++17 feature. There's a branch which is still using `boost::filesystem` so it could be built with VS2013. Check out it if you have only VS2013.
+Webcc depends on `std::filesystem` which is a C++17 feature. There's a branch ([legacy](https://github.com/sprinfall/webcc/tree/legacy)) which is still using `boost::filesystem` so it could be built with VS2013. Check out it if you have only VS2013.
 
 ## Install OpenSSL
 
 Download from [here](http://slproweb.com/products/Win32OpenSSL.html).
 
-The following installers (the "L" might change) are recommended for development:
+The following installers (the "g" might change) are recommended for development:
 
-- Win64 OpenSSL v1.1.0L
-- Win32 OpenSSL v1.1.0L
+- Win64 OpenSSL v1.1.0g
+- Win32 OpenSSL v1.1.0g
 
 During the installation, you will be asked to copy OpenSSL DLLs (`libcrypto-1_1-x64.dll` and `libssl-1_1-x64.dll`) to "The Windows system directory" or "The OpenSSL libraries (/bin) directory". If you choose the later, remember to add the path (e.g., `C:\OpenSSL-Win64\bin`) to the `PATH` environment variable.