guix: utils: Add version-major.

* guix/utils.scm (version-major): New procedure.

guix/utils.scm

@@ -82,6 +82,7 @@ (define-module (guix utils)
             version>=?
             version-prefix
             version-major+minor
+            version-major
             guile-version>?
             string-replace-substring
             arguments-from-environment-variable
@@ -497,6 +498,10 @@ (define (version-major+minor version-string)
 minor version numbers from version-string."
   (version-prefix version-string 2))
 
+(define (version-major version-string)
+  "Return the major version number as string from the version-string."
+  (version-prefix version-string 1))
+
 (define (version>? a b)
   "Return #t when A denotes a version strictly newer than B."
   (eq? '> (version-compare a b)))