On Windows, make `cmd.exe` built-ins and scripts execute through the shell. Closes #449 + generally improves handling for `<sh:exec file="mycript.bat">` type commands on Windows. Note that executing through Windows shell will throw off the rules for command-line quoting...

[egg_info]
tag_build = dev
tag_svn_revision = true

[unittest]
xml_output = build/test-results.xml
coverage_summary = build/test-coverage.txt
coverage_dir = build/coverage