X11 checks in configure phase for some packages

[Fred Dushin]

I've found a few ports that have had issues checking for X11 libraries  
and headers during configuration.  Hacking my way through the  
configure scripts, I've found lines in the checking of X11 libs like:

for ac_extension in a so sl; do

which of course works fine on Solaris, Linux, BSD, and HP/UX.   
Changing this to:

for ac_extension in a so sl dylib; do

fixes the configure phase, and the package then installs properly.

I found this lately with the start-notification package, and I'm  
wonder if I am doing something fundamentally wrong.  There have been  
others like this in the past, but I didn't take record of them.

   Model Name:	MacBook
   Model Identifier:	MacBook2,1
   System Version:	Mac OS X 10.5.5 (9F33)

 > port version
Version: 1.700

XQuartz 2.3.1

I also installed the X11SDK from the Leopard install disk, just to  
make sure.