C++: Set endOffset of Function symbols even if skipping bodies.

Fixes insert-definition-from-declaration when the source file was not
yet opened in an editor.

Change-Id: I4263113390ae4fbe9d4641104b5cb43373ddc5a4
Reviewed-on: http://codereview.qt-project.org/4394


Reviewed-by: Leandro T. C. Melo <leandro.melo@nokia.com>