Change numbers not all linked in output of p4-opened

[gareth-rees]

Running p4-opened produced output like this:

//info.ravenbrook.com/project/mps/master/code/arena.c#1 - integrate change 191196 (text+k)
//info.ravenbrook.com/project/mps/master/manual/source/topic/arena.rst#1 - integrate change 191196 (text)

The change number 191196 was linked for the second line (where the file type is text) but not for the first line (where the file type is text+k).