[LLVMdev] 2.6 Configure doesn't check if OCAMLDOC is missing

[Jianzhou Zhao]

Hi LLVM,

I was installing LLVM2.6 on a system without ocamldoc.
The configure generates OCAMLDOC with value NULL without warnings,
so it got errors at 'make install'. But I did not check if 2.7 fixed
this problem.

-- 
Jianzhou