*8014* Fixed base path issue in IIS

This should fix the base path issue people are reporting in the forum: 

http://pkp.sfu.ca/support/forum/viewtopic.php?f=8&t=11292

I don't have IIS installed but I think I tracked the problem down to different handling of dirname() in IIS and Apache. If someone has IIS running I would appreciate if you could confirm this.