[nc] rename sun to s_un (for building on Solaris)

[Brent Cook]

Finally getting around to trying out nc on some more platforms for
LibreSSL-portable, and ran into Sun/Oracle's silly definition of 'sun'
in the system headers. OK to rename the local sockaddr_un variables?

Portable contains a patch full of #ifdef's around other systems-specific
nc features (e.g. rdomain support). I'm not sure if any of those
should also move into cvs or stay in the portable patch.

Index: netcat.c
===================================================================
RCS file: /cvs/src/usr.bin/nc/netcat.c,v
retrieving revision 1.143
diff -u -p -u -p -r1.143 netcat.c
--- netcat.c    13 Nov 2015 18:13:13 -0000      1.143
+++ netcat.c    22 Nov 2015 22:26:08 -0000
@@ -643,7 +643,7 @@ main(int argc, char *argv[])
 int
 unix_bind(char *path, int flags)
 {
-       struct sockaddr_un sun;
+       struct sockaddr_un s_un;
        int s;

        /* Create unix domain socket. */
@@ -651,17 +651,17 @@ unix_bind(char *path, int flags)
            0)) < 0)
                return (-1);

-       memset(&sun, 0, sizeof(struct sockaddr_un));
-       sun.sun_family = AF_UNIX;
+       memset(&s_un, 0, sizeof(struct sockaddr_un));
+       s_un.sun_family = AF_UNIX;

-       if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
-           sizeof(sun.sun_path)) {
+       if (strlcpy(s_un.sun_path, path, sizeof(s_un.sun_path)) >=
+           sizeof(s_un.sun_path)) {
                close(s);
                errno = ENAMETOOLONG;
                return (-1);
        }

-       if (bind(s, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
+       if (bind(s, (struct sockaddr *)&s_un, sizeof(s_un)) < 0) {
                close(s);
                return (-1);
        }
@@ -737,7 +737,7 @@ tls_setup_server(struct tls *tls_ctx, in
 int
 unix_connect(char *path)
 {
-       struct sockaddr_un sun;
+       struct sockaddr_un s_un;
        int s;

        if (uflag) {
@@ -748,16 +748,16 @@ unix_connect(char *path)
                        return (-1);
        }

-       memset(&sun, 0, sizeof(struct sockaddr_un));
-       sun.sun_family = AF_UNIX;
+       memset(&s_un, 0, sizeof(struct sockaddr_un));
+       s_un.sun_family = AF_UNIX;

-       if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
-           sizeof(sun.sun_path)) {
+       if (strlcpy(s_un.sun_path, path, sizeof(s_un.sun_path)) >=
+           sizeof(s_un.sun_path)) {
                close(s);
                errno = ENAMETOOLONG;
                return (-1);
        }
-       if (connect(s, (struct sockaddr *)&sun, sizeof(sun)) < 0) {
+       if (connect(s, (struct sockaddr *)&s_un, sizeof(s_un)) < 0) {
                close(s);
                return (-1);
        }