[wwwdocs] Fix doc link to x86 built-in functions in gcc-4.8/changes.html

[Gerald Pfeifer]

Somehow X86 apparently was changed to x86 at one point, breaking 
this link.

Fixed thusly.

Gerald

Index: gcc-4.8/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.8/changes.html,v
retrieving revision 1.136
diff -u -r1.136 changes.html
--- gcc-4.8/changes.html	28 Feb 2016 19:39:25 -0000	1.136
+++ gcc-4.8/changes.html	28 Feb 2016 20:43:06 -0000
@@ -589,7 +589,7 @@
       <code>__builtin_cpu_is("westmere")</code> returns a positive integer if
       the run-time CPU is an Intel Core i7 Westmere processor.  Please refer
       to the <a
-      href="https://gcc.gnu.org/onlinedocs/gcc/X86-Built-in-Functions.html#X86-Built-in-Functions">
+      href="https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.html">
       user manual</a> for the list of valid CPU names recognized.</li>
       <li>A built-in function <code>__builtin_cpu_supports</code> has been
       added to detect if the run-time CPU supports a particular ISA feature.