RFR (L) JDK-8230505: Replace JVM type comparisons to T_OBJECT and T_ARRAY with call to is_reference_type

[Lois Foltan]

Please review the following change to call is_reference_type() when 
checking if a type is a T_OBJECT or a T_ARRAY.

open webrev at: 
http://cr.openjdk.java.net/~lfoltan/bug_jdk8230505.0/webrev/index.html
bug link: https://bugs.openjdk.java.net/browse/JDK-8230505

Builds: all tier1 builds, did build with Shenandoah GC, and Solaris builds
Testing: hs-tier1-4 & jdktier1-2 (all platforms), hs-tier5-8 (linux-x64)

Thanks,
Lois