gnu: libxslt: Incorporate grafted patch.

* gnu/packages/xml.scm (libxslt)[replacement]: Remove field.
[source]: Add patch 'libxslt-CVE-2016-4738.patch'.
(libxslt/fixed): Remove variable.

gnu/packages/xml.scm

@@ -135,12 +135,12 @@ project (but it is usable outside of the Gnome platform).")
 (define-public libxslt
   (package
     (name "libxslt")
-    (replacement libxslt/fixed)
     (version "1.1.29")
     (source (origin
              (method url-fetch)
              (uri (string-append "ftp://xmlsoft.org/libxslt/libxslt-"
                                  version ".tar.gz"))
+             (patches (search-patches "libxslt-CVE-2016-4738.patch"))
              (sha256
               (base32
                "1klh81xbm9ppzgqk339097i39b7fnpmlj8lzn8bpczl3aww6x5xm"))
@@ -157,14 +157,6 @@ project (but it is usable outside of the Gnome platform).")
 based on libxml for XML parsing, tree manipulation and XPath support.")
     (license license:x11)))
 
-(define libxslt/fixed
-  (package
-    (inherit libxslt)
-    (name "libxslt")
-    (source (origin
-              (inherit (package-source libxslt))
-              (patches (search-patches "libxslt-CVE-2016-4738.patch"))))))
-
 (define-public perl-graph-readwrite
   (package
     (name "perl-graph-readwrite")