[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

llvm-svn: 263487