[wwwdocs] Update c++-concepts and var-template branches info

[Gabriel Dos Reis]

This patch updates the maintainership of the c++-concepts and
var-template branches.

-- Gaby

Index: svn.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/svn.html,v
retrieving revision 1.188
diff -p -r1.188 svn.html
*** svn.html	18 Aug 2013 20:59:25 -0000	1.188
--- svn.html	14 Sep 2013 00:41:54 -0000
*************** the command <code>svn log --stop-on-copy
*** 542,554 ****
  
    <dt>c++-concepts</dt>
    <dd>This is the sandbox for renewed work on <em>concepts for C++</em>.
!       The branch is maintained by
!       <a href="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</a>.</dd>
  
    <dt>var-template</dt>
    <dd>This branch is for implementation work on 
!       <em>variable template for C++</em>.  It is maintained by
!       <a href="mailto:gdr@gcc.gnu.org">Gabriel Dos Reis</a>.</dd>
  
    <dt>cilkplus</dt>
    <dd>This branch is for the development of
--- 542,556 ----
  
    <dt>c++-concepts</dt>
    <dd>This is the sandbox for renewed work on <em>concepts for C++</em>.
!       It was originally created by Gabriel Dos Reis, with implementation
!       contributed by Andrew Sutton.  It is currently maintained by
!       <a href="mailto:jason@gcc.gnu.org">Jason Merrill</a>.</dd>
  
    <dt>var-template</dt>
    <dd>This branch is for implementation work on 
!       <em>variable template for C++</em>.  It was originally
!        created by Gabriel Dos Reis.  It is maintained by
!       <a href="mailto:jason@gcc.gnu.org">Jason Merrill</a>.</dd>
  
    <dt>cilkplus</dt>
    <dd>This branch is for the development of