[RFR]8215623: Add incremental dump for jmap histo

[臧琳]

Hi All,
       May I ask your help to review this patch for enhance jmap ¨Chisto.
It adds the ¡°incremental¡± arguments that allow jmap ¨Chisto to incrementally save the intermediate data into a temp file.
The intermediate data is dumped incrementally and write to a rolling file, which limit the size of the temp file to be small.
This is useful for user to get intermediate results when jmap/jvm process is killed accidentally. Especially when the heap is large.

This patch is also part of the enhancement described in https://bugs.openjdk.java.net/browse/JDK-8214535.

Webrev: http://cr.openjdk.java.net/~xiaofeya/8215623/webrev.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8215623

Thanks.

BRs,
Lin


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