*stat()-ing symlinks with trailing slashes

[icy at lighttpd.net]

In lighttpd, the decision to process a request as fastcgi or static  
file is configured by specifying either a prefix or suffix to match on  
the requested path.
For example you say "if path ends with .php, process as fastcgi".

In order to find the correct file, lighty needs to open()/stat()  
various combinations. Suppose you have a script foo.php and request  
something like /foo.php/.
Then lighty needs to look for the file (dir) /foo.php/ and if not  
present, /foo.php (php script with / as PATH_INFO).
A normal request will first hit a ENOTDIR for /foo.php/ and then  
succeed at /foo.php (matching the suffix .php) and getting served as  
fastcgi.
Now suppose you have a symbolic link bar.php linked to foo.php and  
request /bar.php/
Without the bug in question, it should behave like the first example  
but as it is now, the open("/bar.php/") succeeds, will not match the  
suffix .php and therefor get served as a static file (sending out the  
source code).
Lighty assumes that there can't be regular files that end in a / (and  
even resolve to the same file without the slash).

We tested various systems and found that FreeBSD, OSX and Solaris < 10  
are affected. Linux, Open/Net/DragonflyBSD, Solaris 10 are not affected.

I'm sure there are other applications (webservers), which too have a  
problem with the described behaviour.