RFR 8235225: Replace CHECK_0 with CHECK_NULL for non-integer returning methods

[Harold Seigel]

Hi,

Please review this change to replace CHECK_0 with CHECK_NULL in 
functions that return oops or pointers and replace CHECK_0 with 
CHECK_false in functions that return bool.

Open Webrev: 
http://cr.openjdk.java.net/~hseigel/bug_8235225/webrev/index.html

JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8235225

The fix was regression tested by running Mach5 tiers 1 and 2 tests and 
builds on Linux-x64, Solaris, Windows, and Mac OS X, by running Mach5 
tiers 3-5 tests on Linux-x64, and JCK lang and VM tests on Linux-x64.

Thanks, Harold