RFR 8220788 [lworld] C1 support for LW2 Arrays

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8220788
http://cr.openjdk.java.net/~iklam/valhalla/8220788-c1-support-for-lw2-arrays.v01/

With this changeset, C1 can properly distinguish between "[QV;" and 
"[LV;" arrays. It can also handle non-flattened arrays that are null 
free (e.g., "[V;" arrays where the size of V is larger than 
ValueArrayElemMaxFlatSize).

Testing:

     cd test/hotspot/jtreg/compiler/valhalla/valuetypes
     jtreg -vmoptions:-XX:+EnableValhallaC1 \
           -vmoptions:-XX:TieredStopAtLevel=1 \
           -vmoptions:-XX:-ValueTypePassFieldsAsArgs \
           -vmoptions:-XX:-ValueTypeReturnedAsFields \
           -Dtest.c1=true \
           .

All tests passed.

My next step is to test C1 more thoroughly, and add test groups for C1 
under valhalla-hs-tier* for mach5 testing.

Thanks
- Ioi