[8u] RFR: 8240676: Meet not symmetric failure when running lucene on jdk8

[Roland Westrelin]

Original bug:
https://bugs.openjdk.java.net/browse/JDK-8240676
https://hg.openjdk.java.net/jdk/jdk/rev/6ccf082f50d4

The context in compile.hpp changed so the original patch requires a
small adjustment. Testing triggered a crash, so I had to cherry-pick the
change in type.cpp line 3996 from an RFE that was integrated in a later
version of the jdk: 8031755 (Type speculation should be used to optimize
explicit null checks).

8u webrev:
http://cr.openjdk.java.net/~roland/8240676.8u/webrev.00/

Testing: x86_64, verified new test fails with the fix commented out,
works otherwise, hotspot/compiler jtreg, some CTW, ran octane with
nashorn.

Roland.