Checking for executables on win32 needs to use the .exe extension.

[Peter Kropf]

When checking for the existance of the graphviz programs on win32 platforms, looking for just the program name isn't enough since windows uses .exe file name extension on executables.

[Shun-ichi Goto]

The problem of the file extension comes from the environment check which does the exact file existance check. How about "try execution then warn if failed" approach instead?

To execute command, extension is not required on windows. So you can make command line without extension like "/path/to/command/dot".

[Peter Kropf]

This was fixed for release v0.3 but will remain open for a little while longer. I'm not certain that how the code was fixed is the right way to get the job done...

[Peter Kropf]

Since there have been no additional comments that the fix doesn't work, I'm going to close this issue. Feel free to open it again if there's a problem...