Remove definition of LLVM_VERSION_INFO; this macro is not used by any of the

files in this directory. If it should be defined anywhere, it should be defined
when building lib/LTO/LTOCodeGenerator.cpp, but we've not had it defined there
for quite some time, so that doesn't really seem to be very important. (It also
would slow down the modules build by creating extra module variants.)

llvm-svn: 218544