msg__control, msg_controllen, and msg_flags in assuan-domain-connect.c

[Martin Traviolia]

I am building libassuan-0.6.10 on Solaris 9 using Sun's 5.6 C compiler.
 
In the file "assuan-domain-connect.c" the fields "msg_control",
"msg_controllen" and "msg_flags" are used from "struct msghdr".

These fields are only defined on Solaris if "_XOPEN_SOURCE" and
_XOPEN_SOURCE_EXTENDED" are defined, or if "_XOPEN_SOURCE" = 500