Allow multiple pop accounts under ONE user login name

This is a Messenger limitation, not a prefs issue; reassigning to mail folks. Phil, please reset the component to messenger when that shows up in Bugzilla.

adding myself to cc: list.

moving to MailNews product.

qa contact -> nbaca

This is a very complex feature, not just a bug so I'm breaking it up into multiple bugs.

This is almost complete, and will be checked in today.

created nsIMsgAccountManager, nsIMsgAccount, nsIMsgIdentity and nsIPop3IncomingServer interfaces and implementations. updated messenger to use new interfaces.

NT4, SeaMonkey build on 4/7/99, Apprunner's browser window shows Build ID 1999040710. - Verified Fixed for Win95 and NT4.0 - The Linux/Mail build is currently not working, I will try to verify when a build is ready. There is no UI but since the latest preferences are working I am marking this verified for NT and Win95. The prefs.js file is in the form of: user_pref("browser.download_directory", "C:\\TEMP\\"); user_pref("browser.startup.homepage_override", false); user_pref("mail.accountmanager.accounts", "account1"); user_pref("mail.account.account1.server", "server1"); user_pref("mail.account.account1.identities", "id1"); user_pref("mail.server.server1.type", "pop3"); user_pref("mail.server.server1.hostname", "dredd"); user_pref("mail.server.server1.userName", "test"); user_pref("mail.server.server1.password", "clear text pop passsword"); user_pref("mail.server.server1.directory", "c:\\program files\\netscape\\users\\test\\mail"); user_pref("mail.identity.id1.fullName", "Mozilla Q. Dragon"); user_pref("mail.identity.id1.organization", "mozilla.org"); user_pref("mail.identity.id1.useremail", "test@netscape.com"); user_pref("mail.identity.id1.smtp_server", "dredd"); user_pref("mail.identity.id1.smtp_name", "test");

Similar preferences work fine for Linux (4/8 build). I'll mark it verified.