Message        <Context> "<name>" is not declared in a scope active
                at this point in the compilation.  However, there is
                a declaration of this identifer with extern storage
                class in another scope at <where>.  This declaration
                will be used.

 Description    In some modes, if the compiler cannot find the
                declaration of an object in the current scope, it
                will search other scopes for extern declarations of
                that object.  If it finds such a declaration, it will
                be used.  Note that this is a language extension
                provided for compatibility with other compilers.

 User Action    Declare the object so that it is visible at all
                places it is referenced.