gnu: Switch to using the version-major procedure.

* gnu/packages/audio.scm (ardour)[arguments]: Switch to using version-major.
  (hmmer)[source]: Switch to using version-major.
  (pidgin)[native-search-paths]: Switch to using version-major.
  (r-minimal)[source]: Switch to using version-major.

gnu/packages/audio.scm

@@ -222,7 +222,7 @@ (define-public ardour
        (modify-phases %standard-phases
          (add-after
           'unpack 'set-rpath-in-LDFLAGS
-          ,(ardour-rpath-phase (version-prefix version 1))))
+          ,(ardour-rpath-phase (version-major version))))
        #:test-target "test"
        #:python ,python-2))
     (inputs

gnu/packages/bioinformatics.scm

@@ -2917,7 +2917,7 @@ (define-public hmmer
        (method url-fetch)
        (uri (string-append
              "http://eddylab.org/software/hmmer"
-             (version-prefix version 1) "/"
+             (version-major version) "/"
              version "/hmmer-" version ".tar.gz"))
        (sha256
         (base32

gnu/packages/messaging.scm

@@ -387,7 +387,7 @@ (define-public pidgin
      (list (search-path-specification
             (variable "PURPLE_PLUGIN_PATH")
             (files (list (string-append "lib/purple-"
-                                        (version-prefix version 1))
+                                        (version-major version))
                          "lib/pidgin")))))
     (home-page "http://www.pidgin.im/")
     (synopsis "Graphical multi-protocol instant messaging client")

gnu/packages/statistics.scm

@@ -114,7 +114,7 @@ (define-public r-minimal
     (source (origin
               (method url-fetch)
               (uri (string-append "mirror://cran/src/base/R-"
-                                  (version-prefix version 1) "/R-"
+                                  (version-major version) "/R-"
                                   version ".tar.gz"))
               (sha256
                (base32