Fix Windows compilation issues

[mikejhill]

First of all, thanks for making and maintaining this. This is a very interesting, fun, and useful tool.

This PR fixes two issues that I ran into trying to build this on Windows:

• The Makefile uses the Unix-friendly classpath delimiters by default. This PR adds a condition for Windows compilation.
• javac doesn't appear to use UTF-8 encoding by default on my system. This causes the following errors during compilation:

  src\analysis\ExploitStringBuilder.java:158: error: unclosed character literal
                                          } else if (currentChar == '╬╡') {
                                                                    ^
  src\analysis\ExploitStringBuilder.java:158: error: unclosed character literal
                                          } else if (currentChar == '╬╡') {
                                                                       ^
  src\analysis\ExploitStringBuilder.java:158: error: not a statement
                                          } else if (currentChar == '╬╡') {
                                                                      ^

  This was addressed by using the codepoint representation instead (\u03b5).

These changes allow the build to succeed on my system (JDK 8, Windows 10).

[NicolaasWeideman]

We updated to Maven, which should resolve the Makefile issue. However, I did merge your commit for using Unicode codepoints, thanks!