clarify licenses for contrib packages

contrib/ANN/README

+See the Copyright.txt and License.txt files for copyright and license
+information.

contrib/Chaco/README

@@ -4,7 +4,14 @@ This software was developed by Bruce Hendrickson and Robert Leland
 at Sandia National Laboratories under US Department of Energy
 contract DE-AC04-76DP00789 and is copyrighted by Sandia Corporation.
 
---------------------------------------------------------------------------------
+
+
+
+/* -----------------------------------------------------------------
+Gmsh - license info and modifications:
+
+Chaco is released under the GNU LGPL v2.1. 
+See http://www.sandia.gov/~bahendr/chaco.html for more info.
 
 Chaco has been slightly modified for integration into the Gmsh program.  Most
 changes are to 'main/interface.c'.  Elsewhere, the 'printf' routine has been
@@ -20,3 +27,5 @@ INTERNAL_VERTICES
 REFINE_MAP
 TERMINAL_PROPOGATION
 
+Gmsh - end 
+----------------------------------------------------------------- */

contrib/MathEval/README

-
 This directory contains a (heavily) modified version of GNU
 libmatheval.
 
+GNU libmatheval is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License as
+published by the Free Software Foundation; either version 2, or (at
+your option) any later version.
+
 The original libmatheval is Copyright (C) 1999, 2002, 2003 Aleksandar
 B. Samardzic
 

contrib/Netgen/README

 
-This directory may contain a slightly modified version of Joachim
+This directory contains a slightly modified version of Joachim
 Sch\"oberl's NETGEN mesh generator:
 
 - only the libsrc directory was kept from the original distribution
@@ -10,12 +10,7 @@ Sch\"oberl's NETGEN mesh generator:
 - the file meshing/meshtype.hpp was slightly modified so that it
   compiles with ISO-C++ complient compilers
 
-**IMPORTANT NOTICE** 
-
-NETGEN requires the boundary mesh to be oriented with exterior
-pointing normals. You HAVE TO define your geometry so that this
-criterion is fulfilled (i.e., correctly orient the geometry surfaces
-and the surface loops).
+See COPYING.LIB for license information
 
 **************************************************************