Revert "Revert "Add implicit null and stack checks for x86""

Fixes x86_64 cross compile issue.  Removes command line options
and property to set implicit checks - this is hard coded now.

This reverts commit 3d14eb620716e92c21c4d2c2d11a95be53319791.

Change-Id: I5404473b5aaf1a9c68b7181f5952cb174d93a90d
diff --git a/compiler/dex/quick/codegen_util.cc b/compiler/dex/quick/codegen_util.cc
index 048aca3..95468d2 100644
--- a/compiler/dex/quick/codegen_util.cc
+++ b/compiler/dex/quick/codegen_util.cc
@@ -1172,9 +1172,12 @@
 }
 
 LIR *Mir2Lir::OpCmpMemImmBranch(ConditionCode cond, RegStorage temp_reg, RegStorage base_reg,
-                                int offset, int check_value, LIR* target) {
+                                int offset, int check_value, LIR* target, LIR** compare) {
   // Handle this for architectures that can't compare to memory.
-  Load32Disp(base_reg, offset, temp_reg);
+  LIR* inst = Load32Disp(base_reg, offset, temp_reg);
+  if (compare != nullptr) {
+    *compare = inst;
+  }
   LIR* branch = OpCmpImmBranch(cond, temp_reg, check_value, target);
   return branch;
 }