[PATCH] Linker: Replace overridden subprograms

[Duncan P. N. Exon Smith]

@Rafael, just realized I never told you why not for these:

> On 2014-Dec-16, at 14:27, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
> 
> 
> +  for (unsigned I = 0, E = CompileUnits->getNumOperands(); I != E; ++I) {
> 
> Can this be a range loop?
> 

Constructor for DICompileUnit from MDNode is explicit. 

> +    for (unsigned S = 0, SE = SPs.getNumElements(); S != SE; ++S) {
> 
> and this one?
> 

DITypedArray doesn't have iteration API.