golang: v↑ (1.5.2)

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

    go1.5.2 (released 2015/12/02) includes bug fixes to the compiler,
    linker, and the mime/multipart, net, and runtime packages

/reviewed-by: TrustMe

component/golang/buildout.cfg

@@ -26,8 +26,8 @@ environment-extra =
 
 [golang15]
 <= golang-common
-url = https://storage.googleapis.com/golang/go1.5.1.src.tar.gz
-md5sum = 4adfbdfca523cc1c229be8a321f3602f
+url = https://storage.googleapis.com/golang/go1.5.2.src.tar.gz
+md5sum = 38fed22e7b80672291e7cba7fb9c3475
 
 # go1.5 needs go1.4 to bootstrap
 environment-extra =