RFR: 8227168: Cleanup usage of NEW_C_HEAP_ARRAY

[Leo Korinth]

Hi!

After I got caught doing an unnecessary check on the return value of 
NEW_C_HEAP_ARRAY (a mistake that I copied) I thought it would be good to 
do a cleanup in the sources so that others would not fall into this 
trap. This is the result.

I have removed some places where the VM will be shut down after 
NEW_C_HEAP_ARRAY returns NULL (it never does return NULL, it does 
instead exit). I have also removed lots of unnecessary casts, that might 
hide bugs.

There are /numerous/ buggy usage that I have NOT fixed. Those are bugs 
that ought to be fixed, but they are not in the gc folder, and I am 
unsure about the best solution (the do not just directly exit the VM). I 
have created a BUG to track them 
(https://bugs.openjdk.java.net/browse/JDK-8230395), and I will leave 
them for others to solve.

I have changed some code paths that I can not test (AIX for example) so 
it would be nice if someone could verify it works there.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8227168

Webrev:
http://cr.openjdk.java.net/~lkorinth/8227168/

Testing:
mach5 tier1-3 (solaris, linux, windows, mac)

Thanks,
Leo