Fix building against texinfo >= 5.0

http://bugs.gentoo.org/514772
http://www.gnu.org/software/texinfo/manual/texinfo/texinfo.html#g_t_0040copyright

--- doc/conduits.texi
+++ doc/conduits.texi
@@ -33,7 +33,7 @@
 
 @page
 @vskip 0pt plus 1filll
-Copyright @copyright 2000 Andrew Arensburger.
+Copyright @copyright{} 2000 Andrew Arensburger.
 
 Permission is granted to make and distribute verbatim copies of
 this manual provided the copyright notice and this permission notice
--- doc/libpalm.texi
+++ doc/libpalm.texi
@@ -57,7 +57,7 @@
 
 @page
 @vskip 0pt plus 1filll
-Copyright @copyright 1999 Andrew Arensburger.
+Copyright @copyright{} 1999 Andrew Arensburger.
 
 Permission is granted to make and distribute verbatim copies of
 this manual provided the copyright notice and this permission notice