ReleaseNotes: Document that LLVM was rewritten in python.

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                            llvm-build

llvm-svn: 156738

llvm/docs/ReleaseNotes.html

@@ -660,6 +660,8 @@ syntax, there are still significant gaps in that support.</p>
    from the previous release.</p>
 
 <ul>
+  <li>LLVM's build system now requires a python 2 interpreter to be present at
+      build time. A perl interpreter is no longer required.</li>
   <li>The C backend has been removed.  It had numerous problems, to the point of
       not being able to compile any nontrivial program.</li>
   <li>The Alpha, Blackfin and SystemZ targets have been removed due to lack of