gitweb: pull ref markes pull out of subject <a> element

gitweb: pull ref markes pull out of subject <a> element

Since 4afbaef (gitweb: ref markers link to named shortlogs, 2008-09-02),
ref markers that accompany the subject in views such as shortlog and
history point to something different from the subject itself. Therefore,
they should not be included in the same <a> element.

Benefits of the change are:

 * better compliance to the XHTML standards, that forbid links within
   links even though the restriction cannot be imposed via DTD; this also
   benefits visualization in some older browsers;

 * when hovering the subject, only the subject itself is underlined; when
   hovering the ref markers, only the text in the hovered ref marker is
   underlined; previously, hovering any written part of the subject column
   led to complete underlying of everything at the same time, with
   unpleasing effects.

Signed-off-by: Giuseppe Bilotta <redacted>
Acked-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>