gnu: GCC@7: Update to 7.4.0.

* gnu/packages/gcc.scm (gcc-7): Update to 7.4.0.
[source](patches): Drop 'gcc-libsanitizer-ustat.patch'.
* gnu/packages/storage.scm (ceph)[inputs]: Change from BOOST to BOOST-CXX14,
as GCC 7.4.0 triggers <https://bugs.gnu.org/33605>.

gnu/packages/gcc.scm

@@ -490,16 +490,15 @@ Go.  It also includes runtime support libraries for these languages.")
 (define-public gcc-7
   (package
     (inherit gcc-6)
-    (version "7.3.0")
+    (version "7.4.0")
     (source (origin
               (method url-fetch)
               (uri (string-append "mirror://gnu/gcc/gcc-"
                                   version "/gcc-" version ".tar.xz"))
               (sha256
                (base32
-                "0p71bij6bfhzyrs8676a8jmpjsfz392s2rg862sdnsk30jpacb43"))
+                "0lgy170b0pp60j9cczqkmaqyjjb584vfamj4c30swd7k0j6y5pgd"))
               (patches (search-patches "gcc-strmov-store-file-names.patch"
-                                       "gcc-libsanitizer-ustat.patch"
                                        "gcc-5.0-libvtv-runpath.patch"))))
     (description
      "GCC is the GNU Compiler Collection.  It provides compiler front-ends

gnu/packages/storage.scm

@@ -321,7 +321,7 @@
        ("python2-testtools" ,python2-testtools)
        ("python2-tox" ,python2-tox)))
     (inputs
-     `(("boost" ,boost)
+     `(("boost" ,boost-cxx14)
        ("curl" ,curl)
        ("cryptsetup" ,cryptsetup)
        ("expat" ,expat)