RFR: JDK-8065371 - Redesign GPIOPortImpl impl in pure java code

[alexey mironov]

issue: https://bugs.openjdk.java.net/browse/JDK-8065371
webrev: http://cr.openjdk.java.net/~amironov/8065371/

Please review the changes made in order to make compatible JavaME pure 
java GPIO realization with native GPIO realization.

Regards,
Alexey