Don't use the symbol name to lookup the symbol value when we can use

Don't use the symbol name to lookup the symbol value when we can use
the symbol index defined by the relocation. The elf_lookup() support
function is to be used by elf_reloc() when symbol lookups need to be
done. The elf_lookup() function operates on the symbol index and
will do a symbol name based lookup when such is required, otherwise
it uses the symbol index directly. This solves the problem seen on
ia64 where the symbol hash table does not contain local symbols and
a symbol name based lookup would fail for those symbols.

Don't pass the symbol name to elf_reloc(), as it isn't used any more.