Add LLVM license info to LICENSE.txt

Author: brson

LICENSE.txt

@@ -236,6 +236,62 @@ included:
   details.
 
 
+* LLVM and Clang. Code for this package is found in
+  src/llvm.
+
+    Copyright (c) 2003-2012 University of Illinois at
+    Urbana-Champaign.  All rights reserved.
+
+    Developed by:
+
+        LLVM Team
+
+        University of Illinois at Urbana-Champaign
+
+        http://llvm.org
+
+    Permission is hereby granted, free of charge, to any
+    person obtaining a copy of this software and associated
+    documentation files (the "Software"), to deal with the
+    Software without restriction, including without
+    limitation the rights to use, copy, modify, merge,
+    publish, distribute, sublicense, and/or sell copies of
+    the Software, and to permit persons to whom the Software
+    is furnished to do so, subject to the following
+    conditions:
+
+        * Redistributions of source code must retain the
+          above copyright notice, this list of conditions
+          and the following disclaimers.
+
+        * Redistributions in binary form must reproduce the
+          above copyright notice, this list of conditions
+          and the following disclaimers in the documentation
+          and/or other materials provided with the
+          distribution.
+
+        * Neither the names of the LLVM Team, University of
+          Illinois at Urbana-Champaign, nor the names of its
+          contributors may be used to endorse or promote
+          products derived from this Software without
+          specific prior written permission.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+    ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+    TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+    PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
+    SHALL THE CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE
+    FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+    ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+    OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+    OTHER DEALINGS WITH THE SOFTWARE.
+
+
+* Additional libraries included in LLVM carry separate
+  BSD-compatible licenses. See src/llvm/LICENSE.txt for
+  details.
+
+
 * Additional copyright may be retained by contributors other
   than Mozilla or the parties enumerated in this file. Such
   copyright can be determined on a case-by-case basis by