Fix for MSVC

[rustyx]

The example doesn't compile in MSVC:

1>\crow\examples\example_vs.cpp(96): error C2838: 'POST': illegal qualified name in member declaration
1>\crow\examples\example_vs.cpp(96): error C2065: 'POST': undeclared identifier
1>\crow\examples\example_vs.cpp(125): error C2838: 'DEBUG': illegal qualified name in member declaration
1>\crow\examples\example_vs.cpp(125): error C2065: 'DEBUG': undeclared identifier

This PR fixes it.

[ioriha]

I encounter this bug today and solve this by your method. Good job!!!