golang: v↑ (1.5.4)

From https://golang.org/doc/devel/release.html#go1.5.minor:

    go1.5.4 (released 2016/04/12) includes two security fixes. It contains
    the same fixes as Go 1.6.1 and was released at the same time. See the Go
    1.6.1 milestone[1] on our issue tracker for details.

    [1] https://github.com/golang/go/issues?q=milestone%3AGo1.6.1

/reviewed-by TrustMe    (tested with helloworld)

component/golang/buildout.cfg

@@ -26,8 +26,8 @@ environment-extra =
 
 [golang15]
 <= golang-common
-url = https://storage.googleapis.com/golang/go1.5.3.src.tar.gz
-md5sum = 80a0eac7ab750b01b3f7096a1d4667b8
+url = https://storage.googleapis.com/golang/go1.5.4.src.tar.gz
+md5sum = a04d570515c46e4935c63605cbd3a04e
 
 # go1.5 needs go1.4 to bootstrap
 environment-extra =