[JITEventListener] Fix some -Wundef warnings

Summary:
This check was added in rL152620, and has started causing downstream warnings in Julia:
```
In file included from /home/tkelman/Julia/julia-0.5/src/codegen.cpp:22:0:
/home/tkelman/Julia/julia-0.5/usr/include/llvm/ExecutionEngine/JITEventListener.h:84:5: warning: "LLVM_USE_INTEL_JITEVENTS" is not defined [-Wundef]
 #if LLVM_USE_INTEL_JITEVENTS
     ^
/home/tkelman/Julia/julia-0.5/usr/include/llvm/ExecutionEngine/JITEventListener.h:100:5: warning: "LLVM_USE_OPROFILE" is not defined [-Wundef]
 #if LLVM_USE_OPROFILE
     ^
```

Patch by Tony Kelman.
Reviewers: loladiro
Differential Revision: http://reviews.llvm.org/D17254

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263487 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ExecutionEngine/JITEventListener.h

@@ -81,7 +81,7 @@ class JITEventListener {
   // Get a pointe to the GDB debugger registration listener.
   static JITEventListener *createGDBRegistrationListener();
 
-#if LLVM_USE_INTEL_JITEVENTS
+#if defined(LLVM_USE_INTEL_JITEVENTS) && LLVM_USE_INTEL_JITEVENTS
   // Construct an IntelJITEventListener
   static JITEventListener *createIntelJITEventListener();
 
@@ -97,7 +97,7 @@ class JITEventListener {
   }
 #endif // USE_INTEL_JITEVENTS
 
-#if LLVM_USE_OPROFILE
+#if defined(LLVM_USE_OPROFILE) && LLVM_USE_OPROFILE
   // Construct an OProfileJITEventListener
   static JITEventListener *createOProfileJITEventListener();