RFR: Fix clang build warnings

[Aleksey Shipilev]

Even though C++ operator precedence rules make this right, clang still complains about mixing && and
||. This makes precedence explicit:

diff -r b6406cc37101 -r b03bb4c0d6e8 src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp
--- a/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp  Tue Oct 30 17:17:00 2018 +0100
+++ b/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp  Thu Nov 01 15:46:15 2018 +0100
@@ -3169,7 +3169,7 @@
   if (n == NULL ||
       n->is_Allocate() ||
       n->bottom_type() == TypePtr::NULL_PTR ||
-      n->bottom_type()->make_oopptr() != NULL && n->bottom_type()->make_oopptr()->const_oop() !=
NULL) {
+      (n->bottom_type()->make_oopptr() != NULL && n->bottom_type()->make_oopptr()->const_oop() !=
NULL)) {
     return NotNeeded;
   }
   if (n->is_Phi() ||

Testing: Mac OS X builds

Thanks,
-Aleksey