RFR: JDK-8056080 - GPIO DIR_BOTH_INIT_INPUT and DIR_BOTH_INIT_OUTPUT are not supported

[alexey mironov]

issue: https://bugs.openjdk.java.net/browse/JDK-8056080
webrev: http://cr.openjdk.java.net/~alkonsta/8056080

Hi All,

Please review the changes made in order to add opportunity change 
direction of GPIO.

Regards,
Alexey