version() abuse! Note of library writers.

[Anders F Björklund]

Sean Kelly wrote:
> It may help to think about weird configurations like targeting Cygwin
> on Windows (where Windows, Win32, and Posix may theoretically be
> defined) or WINE on Linux (where linux and Win32 may be defined).

Something is broken if "Windows" is declared in Cygwin,
or if "linux" is declared when running under Wine...

--anders