Oops, fix reporting for multiple sub calls in the same line
Treat a configurable set of slow opcodes as if they were subroutines
Display XSUBs as a list at the bottom of the file report, under opcodes

Since XSUBs do not have any meaningful mapping to Perl files, just display them
in the same file as other subs from the same package, and failing that, in a
special 'no-file' "file".
Don't call SvGETMAGIC() twice, and document that &{} overload might be called twice