IUPAC naming of isocyanides
The most recent IUPAC recommendations[1] states that:


  P-61.9: Preferred IUPAC names are formed substitutively using the prefix ‘isocyano’ attached directly to a parent hydride. 


This is a change from previous recommendations, and differs from some of your examples above. 

To give a concrete example, $\ce{C6H5NC}$ should be named isocyanobenzene - this is known as a PIN by IUPAC (preferred IUPAC name). Phenylisocyanide is also acknowledged as an acceptable trivial name (a name that does not conform to the recommendations but is still commonly used).  

[1]: IUPAC Recommendations for Preferred Names 2013, Chapter P-6. DOI:10.1039/9781849733069-00648