Generate additional desc_signature node for function templates
Generate additional desc_signature node for function templates

We need to render templates on two lines but desc_signature doesn't
permit multiple lines. So add two desc_signature nodes for function
templates, one for template <...> part and another for the rest.

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