fix test-flags definition for Windows

We need to quote a classpath with a Windows path separator (';') so it
isn't interpreted by the shell.
fix portability problem in Strings test

There was a test in Strings.java that assumed the default character
encoding was UTF-8, which is an invalid assumption on some platforms
(e.g. Windows).  This modifies the test to specify the encoding
explicitly.
Merge pull request #257 from dicej/windows

Windows fixes