RFR: JDK-8054922 - UART timeout and threshold & JDK-8053930 - UART always returns 7 bit per char

[Jen Dority]

issues: JDK-8053930 <https://bugs.openjdk.java.net/browse/JDK-8053930> & 
JDK-8054922 <https://bugs.openjdk.java.net/browse/JDK-8054922>
webrev: http://cr.openjdk.java.net/~jld/8054922/

Hi All,

Need a review for an update to the UART code. These changes  add a 
timeout event, reorganize the the uart ccode, and fix a few bugs with 
the UART event handling that were found while testing these changes.

Thanks,
Jen