[wwwdocs] Added /gcc-7/porting_to.html

[Gerald Pfeifer]

On Mon, 30 Jan 2017, Jonathan Wakely wrote:
> This adds the porting to guide for GCC 7. So far it only has details
> of C++ changes, mostly in the std::lib.

Thanks for doing that, Jonathan!

One minor observation: This has references to the GCC 5 and GCC 6
release notes, where the latter is a relative link and the former
an absolute.  

I assume that was not intentional, and applied the patch below
after verifying that neither maintainer-scripts/gcc_release nor
contrib/gennews actually package porting_to.html.

Gerald

Index: gcc-7/porting_to.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-7/porting_to.html,v
retrieving revision 1.2
diff -u -r1.2 porting_to.html
--- gcc-7/porting_to.html	30 Jan 2017 17:58:52 -0000	1.2
+++ gcc-7/porting_to.html	3 Feb 2017 07:53:45 -0000
@@ -116,7 +116,7 @@
 <p>
 When iostream objects are requested to throw exceptions on stream buffer
 errors, the type of exception thrown has changed to use the
-<a href="https://gcc.gnu.org/gcc-5/changes.html#libstdcxx">new libstdc++ ABI
+<a href="../gcc-5/changes.html#libstdcxx">new libstdc++ ABI
 introduced in GCC 5</a>. Code which does
 <code>catch (const std::ios::failure&)</code> or similar will not catch
 the exception if it is built using the old ABI. To ensure the exception is