[7u4] Request for phase 2 approval for bulk integration of hs23-b21

[John Coomes]

Requesting approval to integrate hs23-b21 into jdk7u4-b20.

A webrev is available at:

http://cr.openjdk.java.net/~jcoomes/7u4/hs23-b21-jdk7u4-b20.webrev/

SQE is evaluating the fixes; the integration will proceed only after
SQE has approved.

The fixes in the proposed integration are below.  The fix for 7159766
simply disables tiered compilation by default.  It has undergone
nightly testing, but is not in a jdk8 repository because we plan to
resolve the performance regressions while keeping tiered compilation
enabled in jdk8.  However, that is too risky for jdk7u4.

7158135: new hotspot build - hs23-b21
7159766: Tiered compilation causes performance regressions

-John