Fix extensible class linting errors on IA32

[0xdaryl]

On IA32 Linux, the following errors are reported by the linter tool. Note these errors are found when running this tool on 32-bit Linux, which is not part of the Travis CI validation.

The fix involves adding a downcast scope qualifier (to TR::TreeEvaluator::) when calling a static member function.

$ PLATFORM=amd64-linux-gcc make -f linter.mk -j20 ../../fvtest/compilertest/x/codegen/Evaluator.cpp.linted
 In file included from ../../fvtest/compilertest/x/codegen/Evaluator.cpp:19:
../../compiler/x/i386/codegen/OMRTreeEvaluator.cpp:103:4: error: Static member function must be called with scope qualifier. Suggested fix:
   compareGPRegisterToImmediate(node, cmpRegister->getHighOrder(), highValue, cg);
   ^
   TR::TreeEvaluator::
../../compiler/x/i386/codegen/OMRTreeEvaluator.cpp:107:4: error: Static member function must be called with scope qualifier. Suggested fix:
   compareGPRegisterToImmediate(node, cmpRegister->getLowOrder(), lowValue, cg);
   ^
   TR::TreeEvaluator::
../../compiler/x/i386/codegen/OMRTreeEvaluator.cpp:153:7: error: Static member function must be called with scope qualifier. Suggested fix:
      compareGPRegisterToImmediate(node, cmpRegister->getHighOrder(), highValue, cg);
      ^
      TR::TreeEvaluator::
../../compiler/x/i386/codegen/OMRTreeEvaluator.cpp:163:7: error: Static member function must be called with scope qualifier. Suggested fix:
      compareGPRegisterToImmediate(node, cmpRegister->getLowOrder(), lowValue, cg);
      ^
      TR::TreeEvaluator::
../../compiler/x/i386/codegen/OMRTreeEvaluator.cpp:222:7: error: Static member function must be called with scope qualifier. Suggested fix:
      compareGPRegisterToImmediate(node, cmpRegister->getHighOrder(), highValue, cg);
      ^

[0xdaryl]

Note that the line numbers are slightly off in the above output because the copyright header was changed in the meantime. The offending lines are easy to find though.