Modify new attribute from previous patch so that it is necessary only on extensions with split names.  Tested with diff and found no difference with previous stylesheet header-file output.
Modify new attribute from previous patch so that it is necessary only on
extensions with split names.  Tested with diff and found no difference with
previous stylesheet header-file output.

stapelberg/libxcb,OpenInkpot-archive/iplinux-libxcb,OpenInkpot-archive/iplinux-libxcb,topcat/xcb-win32,topcat/xcb-win32,topcat/xcb-win32,OpenInkpot-archive/iplinux-libxcb,stapelberg/libxcb,stapelberg/libxcb,topcat/xcb-win32,topcat/xcb-win32