[BUILD] fix build on Solaris due to recent log changes

[BUILD] fix build on Solaris due to recent log changes

Solaris, as well as many other unixes doesn't know about sun_len
for UNIX domain sockets. It does not honnor the __SOCKADDR_COMMON
macro either. After looking at MacOS-X man (which is the same as
BSD man), OpenBSD man, and examples on the net, it appears that
those which support sun_len do not actually use it, or at least
ignore it as long as it's zero. Since all the sockaddr structures
are zeroed prior to being filled, it causes no problem not to set
sun_len, and this fixes build on other platforms.

Another problem on Solaris was that the "sun" name is already
defined as a macro returning a number, so it was necessary to
rename it.