Encoding of source files unclear

In [InvokeDynamicCP.java:28](https://github.com/Sable/jasmin/blob/96accfb59e1b32eddc8e55cfcef43fa7d9c7f567/lib/jas/src/jas/InvokeDynamicCP.java#L28) and in [MethodHandleCP.java:27](https://github.com/Sable/jasmin/blob/96accfb59e1b32eddc8e55cfcef43fa7d9c7f567/lib/jas/src/jas/MethodHandleCP.java#L27) there are ISO-8559-15 characters (the € sign).

This causes warnings when I do a build on my (Linux) machine (default charset is UTF-8 here):
```
    [javac] /tmp/sableJasmin/jasmin/lib/jas/src/jas/InvokeDynamicCP.java:28: warning: unmappable character for encoding UTF8
    [javac]     uniq = (bsmClassName + "fv0�" + bsmName + "&%$91&" + bsmSig+ "*(012$" + methodName + "dfg8932" + methodSig).intern();
    [javac]                                ^
    [javac] /tmp/sableJasmin/jasmin/lib/jas/src/jas/MethodHandleCP.java:27: warning: unmappable character for encoding UTF8
    [javac]     uniq = kind + "$gfd�" + ownerName + "&%$91&" + fieldOrMethodName + "*(012$" + sig;
    [javac]                        ^
```
I suppose this is not on purpose. To solve this one of the following could be done:

1. Replace the euro sign with an escape sequence (`\u20ac`)
2. Specify `encoding="ISO-8559-15"` in the ANT-javac-Task

I'd be glad to create a pull request if you tell me which of the two it is supposed to be.