Add an annotated source view to the performance-log viewer's
profile view.  When selecting the [Self] entry of a function's
profile, for which source information is available and whose source
is found locally, a new column opens, showing the function's
source, annotated with sample statistics.  Header-bar buttons allow
navigation through the annotated lines, selection of all the
samples corresponding to a given line, and opening the text editor
at the current line.