[glib] gcredentialsprivate: clarify the USE_FREEBSD_CMSGCRED users

[Dan Winship <danw src gnome org>]

commit e8d3f29300b695b1f49723fc561f3ab81a1fb361
Author: Dan Winship <danw gnome org>
Date:   Tue Jan 27 07:38:31 2015 -0500

    gcredentialsprivate: clarify the USE_FREEBSD_CMSGCRED users
    
    Add comments clarifying what the three non-FreeBSD platforms using
    G_CREDENTIALS_USE_FREEBSD_CMSGCRED are.

 gio/gcredentialsprivate.h |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/gio/gcredentialsprivate.h b/gio/gcredentialsprivate.h
index 8387638..e156276 100644
--- a/gio/gcredentialsprivate.h
+++ b/gio/gcredentialsprivate.h
@@ -31,7 +31,10 @@
 #define G_CREDENTIALS_SOCKET_GET_CREDENTIALS_SUPPORTED 1
 #define G_CREDENTIALS_SPOOFING_SUPPORTED 1
 
-#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__GNU__) || defined(__DragonFly__)
+#elif defined(__FreeBSD__)                                  || \
+      defined(__FreeBSD_kernel__) /* Debian GNU/kFreeBSD */ || \
+      defined(__GNU__)            /* GNU Hurd */            || \
+      defined(__DragonFly__)      /* DragonFly BSD */
 #define G_CREDENTIALS_SUPPORTED 1
 #define G_CREDENTIALS_USE_FREEBSD_CMSGCRED 1
 #define G_CREDENTIALS_NATIVE_TYPE G_CREDENTIALS_TYPE_FREEBSD_CMSGCRED