The bitmap is different for a prototype (declaration) vs. a function (definition). fx
There is also an option to prioritize navigation to the symbol definition, then Ctrl+Dot will take you directly to the definition (provided there is only one). If there are multiples, you will be prompted with both prototypes and function definitions, because, gosh, if you are going to have to choose anyway, why not have ALL the choices, you know, sometimes you do need to get to the prototype too!
Another feature to pay attention to is that when you hit Ctrl+Dot and select and item from the list, look at the message line, you can hit Ctrl+Dot again to cycle through the other items in the list, and Ctrl+Comma to cycle backwards through the list. This stays in effect until you do something other than Ctrl+Dot or Ctrl+Comma.