Add OSX support, buildable via "make osx".

Make sure you have OpenSSL 1.0.0d+ (available from Macports) installed.

Based on diff from Vaibhav Bhembre via github

Makefile

@@ -22,6 +22,9 @@ linux:
 bsd:
 	@S_SRC=src/bsd.c make kore
 
+osx:
+	@LDFLAGS="-L/opt/local/lib" CFLAGS="-I/opt/local/include/" make bsd
+
 kore: $(S_OBJS)
 	$(CC) $(CFLAGS) $(S_OBJS) $(LDFLAGS) -o $(BIN)
 

src/bsd.c

@@ -147,5 +147,7 @@ kore_platform_disable_accept(void)
 void
 kore_platform_proctitle(char *title)
 {
+#ifndef __MACH__
 	setproctitle("%s", title);
+#endif
 }

src/worker.c

@@ -179,8 +179,14 @@ kore_worker_entry(struct kore_worker *kw)
 		fatal("cannot chroot(): %s", errno_s);
 	if (chdir("/") == -1)
 		fatal("cannot chdir(): %s", errno_s);
-	if (setgroups(1, &pw->pw_gid) || setresgid(pw->pw_gid, pw->pw_gid,
-	    pw->pw_gid) || setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
+	if (setgroups(1, &pw->pw_gid) ||
+#ifdef __MACH__
+	    setgid(pw->pw_gid) || setegid(pw->pw_gid) ||
+	    setuid(pw->pw_uid) || seteuid(pw->pw_uid))
+#else
+	    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
+	    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
+#endif
 		fatal("unable to drop privileges");
 
 	snprintf(buf, sizeof(buf), "kore [wrk %d]", kw->id);