golang: v↑ to go1.10

Drop support for Go 1.8; Add support for Go 1.10 and make it the
default.

It comes a bit late because previously we were hitting
https://golang.org/issues/24285, and so have beeing waiting for
nexedi/slapos.core!42 to be
deployed there on slapos nodes everywhere.

As of 9 Aug 2018 it seems that deployment has been completed.

/reviewed-by @alain.takoudjou, @rafael.
/reviewed-on nexedi/slapos!372

component/golang/buildout.cfg

@@ -33,21 +33,21 @@ environment-extra =
 make-targets= cd src && ./make.bash && cp -alf .. ${:location}
 
 
-[golang18]
+[golang19]
 <= golang-common
-url = https://dl.google.com/go/go1.8.7.src.tar.gz
-md5sum = c61cfe9c85e7d42f903d3fe146d7cde6
+url = https://dl.google.com/go/go1.9.4.src.tar.gz
+md5sum = 6816441fd6680c63865cdd5cb8bc1960
 
-# go1.8 needs go1.4 to bootstrap
+# go1.9 needs go1.4 to bootstrap
 environment-extra =
   GOROOT_BOOTSTRAP=${golang14:location}
 
-[golang19]
+[golang1.10]
 <= golang-common
-url = https://dl.google.com/go/go1.9.4.src.tar.gz
-md5sum = 6816441fd6680c63865cdd5cb8bc1960
+url = https://dl.google.com/go/go1.10.3.src.tar.gz
+md5sum = d15dfb264105c5e84fbe33f4a4aa5021
 
-# go1.9 needs go1.4 to bootstrap
+# go1.10 needs go1.4 to bootstrap
 environment-extra =
   GOROOT_BOOTSTRAP=${golang14:location}
 
@@ -84,7 +84,7 @@ bin	= ${:directory}/bin
 depends = ${gowork.goinstall:recipe}
 
 # go version used for the workspace (possible to override in applications)
-golang  = ${golang19:location}
+golang  = ${golang1.10:location}
 
 # no special build flags by default
 buildflags =