Cannot use on AIX

[bommo1]

java.lang.IllegalStateException: Cannot evaluate OS constant for current operating system: AIX
	at org.unix4j.util.OS.current(OS.java:46) ~[unix4j-base-0.6.jar!/:na]
	at org.unix4j.util.FileUtil.isWindows(FileUtil.java:28) ~[unix4j-base-0.6.jar!/:na]
	at org.unix4j.util.FileUtil.<clinit>(FileUtil.java:25) ~[unix4j-base-0.6.jar!/:na]
	at org.unix4j.io.FileInput.getFileInfo(FileInput.java:147) ~[unix4j-base-0.6.jar!/:na]

As I see in the code only Windows is treated differently.
Please add AIX (and maybe OTHER) in the enum.

Thank you!

[terzerm]

Thanks for reporting this and for the pull request. Looks good at quick glance --- will check in more detail e.g. what impact Other has.
Will keep you posted.

[terzerm]

Fixed in a slightly different way, but thanks for reporting and for the pull request.