gnu: Use the 'patches' field of <origin>.

* gnu/packages/apr.scm,
  gnu/packages/autotools.scm,
  gnu/packages/avahi.scm,
  gnu/packages/cdrom.scm,
  gnu/packages/cmake.scm,
  gnu/packages/cpio.scm,
  gnu/packages/cross-base.scm,
  gnu/packages/emacs.scm,
  gnu/packages/flex.scm,
  gnu/packages/fontutils.scm,
  gnu/packages/glib.scm,
  gnu/packages/grub.scm,
  gnu/packages/guile.scm,
  gnu/packages/idutils.scm,
  gnu/packages/libevent.scm,
  gnu/packages/linux.scm,
  gnu/packages/mail.scm,
  gnu/packages/make-bootstrap.scm,
  gnu/packages/mp3.scm,
  gnu/packages/oggvorbis.scm,
  gnu/packages/pdf.scm,
  gnu/packages/plotutils.scm,
  gnu/packages/qemu.scm,
  gnu/packages/recutils.scm,
  gnu/packages/rush.scm,
  gnu/packages/scheme.scm,
  gnu/packages/system.scm,
  gnu/packages/tcsh.scm,
  gnu/packages/valgrind.scm,
  gnu/packages/vpn.scm,
  gnu/packages/w3m: Use the 'patches' field of <origin> instead of
  adding a patch as input plus using #:patches.

gnu/packages/plotutils.scm

@@ -35,15 +35,13 @@
                                  version ".tar.gz"))
              (sha256
               (base32
-               "1arkyizn5wbgvbh53aziv3s6lmd3wm9lqzkhxb3hijlp1y124hjg"))))
+               "1arkyizn5wbgvbh53aziv3s6lmd3wm9lqzkhxb3hijlp1y124hjg"))
+             (patches (list (search-patch "plotutils-libpng-jmpbuf.patch")))))
     (build-system gnu-build-system)
-    (arguments '(#:patches (list (assoc-ref %build-inputs "patch/jmpbuf"))))
     (inputs `(("libpng" ,libpng)
               ("libx11" ,libx11)
               ("libxt" ,libxt)
-              ("libxaw" ,libxaw)
-              ("patch/jmpbuf"
-               ,(search-patch "plotutils-libpng-jmpbuf.patch"))))
+              ("libxaw" ,libxaw)))
     (home-page
      "http://www.gnu.org/software/plotutils/")
     (synopsis "Plotting utilities and library")