Fix rendering of overloaded functions
Fix rendering of overloaded functions

Move the code that retrieves function signature to the render method
because it can be called from different places depending on whether
there is one or multiple matches. Also don't modify the directive
arguments in place because render may be called multiple times.

AnthonyTruchet/breathe,RR2DO2/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,RR2DO2/breathe,kirbyfan64/breathe