I defined a javascript library (tinyscrollbars) via an info file in the directory "sites/all/libraries/jquery/tinyscrollbars". JQP correctly found this and included it in its configuration.

I looked at what could be changed under the admin/build menu, and having decided that I did not want to "reset" anything, I clicked "sumbit".

I later noticed that every page had an entry

  <script type="text/javascript" src="/1?x"></script>

in addition to the entry for tinyscrollbars.

I tracked this down to the fact that the entry in the system table includes a "changed=1" value in the serialized info field.

This appears to be cause the $library returned to function "drupal_add_library" to contain the entries

[info][scripts][0] => array(
  [jquery.tinyscrollbar.min.js] = sites/all/libraries/jquery/tinyscrollbar/jquery.tinyscrollbar.min.js
  [changed] = 1
)

Then when this is run through the foreach loops later in that function, two calls to "drupal_add_js" are made for the two entries, resulting in the bogus javascript file include.

The unwanted entry can be removed by "resetting" the javascript library entries (rebuild the cache?), which is not a problem for me, but is someone had actually changed the details and needed those changes, then this would be a bigger issue.