New function citation() to display citation information (patch #7960) * display_info_file.m: the new function is pretty much the same as news() so this new private function is their common code * citation.m: the new function * help.m: changed to use the private function with common code with citation() * CITATION: new file with citation instructions for Octave core * Makefile.am: add CITATION file into the build system and install into octetc * bootstrap.conf: make sure that the CITATION is present when installing * copy_files.m: make pkg() check and install CITATION files from packages * doc/interpreter/package.txi: document optional CITATION files for packages

--- a/bootstrap.conf	Sat Mar 02 19:31:26 2013 -0500
+++ b/bootstrap.conf	Sun Mar 03 02:34:44 2013 +0000
@@ -156,7 +156,7 @@
   ## with building the rest of Octave, and INSTALL, which is linked from
   ## gnulib/doc/INSTALL by the bootstrap script.
 
-  for f in NEWS README COPYING; do
+  for f in NEWS README COPYING CITATION; do
     if ! test -f $f; then
       echo "required file $f is missing" 2>&1
       exit 1