RFR: JDK-8242804 Fix trivial deprecation issues in jdk.hotspot.agent

[Magnus Ihse Bursie]

In the quest for getting rid of warning messages in jdk.hotspot.agent, 
the time has now come for another major source of deprecation messages, 
that are trivial to fix and might hide more tricky issues.

This patch handles the "new Integer(42)" pattern of explicit boxing, 
which is deprecated. I have fixed this using the improved autoboxing 
functionality in modern Java (e.g. just "42"), wherever possible (which 
was most places). For some cases, a modern factory method was preferable.

This patch also fixes newInstance() deprecation.

As with the previous patches, it might be easier to just read the patch 
file, 
http://cr.openjdk.java.net/~ihse/JDK-8242804-SA-boxing-deprecations/webrev.01/open.patch. 
(Fortunately, there are a log less changes in this patch than the 
previous ones.)

Bug: https://bugs.openjdk.java.net/browse/JDK-8242804
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8242804-SA-boxing-deprecations/webrev.01

/Magnus