For people learning LLVM, the isExternal() method on Function can be confusing. It gets confused with isExternalLinkage(). To make things more clear in the code, I suggest we rename this to isDeclaration() or isPrototype(). This keeps it clear from using the word External which can cause the confusion. There's no functional change implied by this, just a name change.
sounds like a good idea to me!
Fixed.