Update backupdb.php

handle wasn't being closed
Fixes #544 'Possibly related threads' and 'Only view own threads'
Fixes #517 'emailpmnotify' causes SQL error
Update recount_rebuild.php

Fixes issue #623.  If a negative value is entered, it reverts to the default value.
Merge pull request #608 from PaulBender/fix-517

Fixes #517 'emailpmnotify' causes SQL error
Merge pull request #635 from dragonexpert/fix-623

Update recount_rebuild.php
Add CONTRIBUTING.md
Merge pull request #604 from Stefan-ST/fix-544

Fixes #544 'Possibly related threads' and 'Only view own threads'
Update backupdb.php
Merge pull request #486 from RageSmirk/patch-1

Handle isn't closed properly in backupdb.php