SO_REUSEADDR and multicast sockets with LuaSocket

[joseph stewart <joseph.stewart@...>]

Hello Diego and list:

I've been playing with multicast sockets under C and Lua.

I just noticed that under OSX, the socket option SO_REUSEADDR doesn't  
behave the same as Linux... that is I cannot open multiple listeners  
on the same multicast address (group).

A quickly banged-out fix was to change SO_REUSEADDR in luasocket/src/ 
options.c to SO_REUSEPORT. In my local C code, I use the __APPLE__  
define to make this conditionally compile under both Linux and OSX.

I'll see if I can find out why OSX has this behavior, but in the  
meantime... this is a quick fix for me that I thought might help  
someone else out there!

Blessings,

-joe