localrepo: eliminate local requirements var in init Localrepo's __init__ function creates a local requirements set to add to before it replaces the instance's set with it. This is unnecessary, so let's just use the instance's set directly.

localrepo: rename requirements parameter in stream_in() To avoid confusion from overloading of the variable name "requirements", the requirements is renamed to remotereqs for localrepo's stream_in() function.

localrepo: have stream_in() not modify its argument Localrepo's stream_in function modified its requirements argument. This is not good practice because it may be unexpected behavior to the caller.