[DotGNU]pnet on os x

[Ian Fung]

i recently tried to compile and install pnet on OS X (10.2.6). It gave 
me an error about socklen_t not being defined in socket.c. socklen_t is 
in /usr/include/sys/socket.h on os x. to fix this, i put a #define 
_BSD_SOCKLEN_T_ in pnet/support/socket.c.

now everything compiles and runs correctly.

-alias