Handle early access JDK versions

Yeah, I do run with early access JDK versions.
I'm a pita, I know, but we might be legion out there.

```
java.lang.NumberFormatException: For input string: "60-ea"
	at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.lang.Integer.parseInt(Integer.java:492)
	at java.lang.Integer.parseInt(Integer.java:527)
	at org.boon.core.Sys.<clinit>(Sys.java:85)
	at org.boon.collections.LazyMap.buildIfNeeded(LazyMap.java:130)
	at org.boon.collections.LazyMap.containsKey(LazyMap.java:116)
```