doc: add licence text in final document

doc/starpu.texi

@@ -23,7 +23,7 @@ Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3
 or any later version published by the Free Software Foundation;
 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
-See the GNU Free Documentation License in @file{COPYING.GFDL} for more
+See the GNU Free Documentation License in @ref{Licence} for more
 details.
 @end quotation
 @end copying
@@ -5070,6 +5070,10 @@ static struct starpu_sched_policy_s dummy_sched_policy = @{
 
 @include vector_scal_opencl_codelet.texi
 
+@node Licence
+@appendix GNU Free Documentation License
+@include COPYING.GFDL
+
 @c
 @c Indices.
 @c