Add early support for a plugin feature.  'hpclink --plugin name' looks for the script 'name' in lib/hpctoolkit/plugins/ to source.  The script should follow sh syntax and define these variables.
Add early support for a plugin feature.  'hpclink --plugin name' looks
for the script 'name' in lib/hpctoolkit/plugins/ to source.  The
script should follow sh syntax and define these variables.

hpclink_files='...'
hpclink_wrap_names='...'

So far, only hpclink uses this feature.  This feature is still early
and somewhat in flux.  And we may need to establish some convention on
variable names to avoid name clashes.

zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit