MacOS: gosxcontenttype.c consider generic icon names also
MacOS: gosxcontenttype.c consider generic icon names also

This patch considers generic icon names also when icon names
are searched based on content type. Without this fix only
non-generic icon names are found. This results in no icons
for pdf and jpeg files in the file selection dialog.
This is discussed in

https://bugzilla.gnome.org/show_bug.cgi?id=788936

johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib