patch submitted by rufus@nonstuff.de (Rufus)
call QuoteXMLChars on bug_file_loc and attachment desc

logged in yet.  Thanks to luke_harless@attglobal.net for discovering this
one.

add whoid usergroupset comment query to bug data fields
add AppendComment function
add CanChangeField function to check if a person can change a field
add display() for quick dumps of the bug
add Collision to check for midair collisions before changing a bug
added a stub function for changing a bug in the database
init_bug will now take either a userid or an e-mail address as a valid parameter

contributed by dave@intrec.com (Dave Miller)

experimental: Not part of normal bugzilla distibution. Bug.pm creates a bug object and provides methods for getting and setting attributes and for printing out the bug as xml. xml.cgi prompts for a list of bugs and displays the list as html. xml.cgi replaces export_bug.cgi