Fixing inline requests for `snowcrash` usage with MSVC

To resolve linking problem on `snowcrash`.

CC. @zdne.
What do you mean by  "there is a condition" ? 

Isn't `_MSC_VER` defined when building on windows? So if I read it correctly since pretty much every file includes the `buffer.h` the `inline` was defined as nothing and so the functions weren't inlined.