Update svn.html documentation

Update svn.html documentation

[Michael Meissner]

It was pointed out to me that the section on svn branches was out of date WRT
to the ibm/* branches.  I have checked in this change:

Index: htdocs/svn.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/svn.html,v
retrieving revision 1.220
diff -p -c -r1.220 svn.html
*** htdocs/svn.html	23 May 2018 09:02:54 -0000	1.220
--- htdocs/svn.html	23 May 2018 19:04:49 -0000
*************** be prefixed with the initials of the dis
*** 658,682 ****
    <a href="mailto:cmtice@google.com">cmtice@google.com</a>.
    </dd>
  
!   <dt>ibm/gcc-4_1-branch</dt>
!   <dd>This branch provides decimal float support backported to GCC 4.1.x.
!   It is expected to be used primarily within IBM for PowerPC-64 GNU/Linux.
!   The branch is maintained by Janis Johnson
!   &lt;<a href="mailto:janis@us.ibm.com">janis@us.ibm.com</a>&gt;.</dd>
! 
!   <dt>ibm/gcc-4_3-branch</dt>
!   <dd>This branch is expected to be used primarily within IBM for
!   PowerPC-64 GNU/Linux.</dd>
! 
!   <dt>ibm/gcc-4_4-branch</dt>
!   <dd>This branch is expected to be used primarily within IBM for
!   PowerPC-64 GNU/Linux.</dd>
! 
!   <dt>ibm/power7-meissner</dt>
!   <dd>This branch is a private development branch for Power7 (PowerPC ISA 2.06)
!   development, prior to the patches being submitted to the mainline.
!   The branch is maintained by Michael Meissner,
!   <a href="mailto:meissner@linux.vnet.ibm.com">meissner@linux.vnet.ibm.com</a>.</dd>
  
    <dt>linaro/gcc-<em>x_y</em>-branch</dt>
    <dd>Linaro compilers based on GCC <em>x.y</em> releases.  These branches
--- 658,667 ----
    <a href="mailto:cmtice@google.com">cmtice@google.com</a>.
    </dd>
  
!   <dt>ibm/gcc-<em>x</em>-branch</dt>
!   <dd>Branches that track the GCC branches and are used to create the
!   IBM Advance Toolchain releases.  This family of branches is maintained by
!   personnel from IBM.</dd>
  
    <dt>linaro/gcc-<em>x_y</em>-branch</dt>
    <dd>Linaro compilers based on GCC <em>x.y</em> releases.  These branches


-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.ibm.com, phone: +1 (978) 899-4797