Restore the Xcode rules to the Objective-C template as per the discussion
thread on 5bd4330b. Although the rules correspond to an IDE and so are
global, most users of the Obj-C template expect to find the Xcode rules
in the template generated by github.com, since the IDE is so ubiquitous.

This could possibly be resolved by adding a template transclusion
mechanism in the future, but for now duplication is the way to go.