RFR 4823133: RandomAccessFile.length() is not thread-safe

[vyom]

Hi All,

Please review my changes for below bug.

Bug: JDK-4823133 : RandomAccessFile.length() is not thread-safe

Webrev:http://cr.openjdk.java.net/~vtewari/4823133/webrev0.0/ 
<http://cr.openjdk.java.net/%7Evtewari/4823133/webrev0.0/>

This change ensure that  length() does not temporarily changes the file pointer and it will make sure that there is no race
condition in case of multi thread uses.

Thanks,
Vyom