Add missing reference to jenkins.

Move design.mps.tests from old to current section of the manual.

Copied from Perforce
 Change: 195102

mps/design/tests.txt

@@ -297,6 +297,8 @@ PC at the Ravenbrook office) runs the ``testci`` target on platforms
 w3i3mv and w3i6mv whenever there is a commit to the `mps GitHub
 repository`_.
 
+.. _Jenkins: https://jenkins.io
+
 _`.ci.jenkins.config`: There are instructions for installing and
 configuring Jenkins in [GDR_2016-04-14]_, [GDR_2016-04-15]_ and
 [GDR_2016-04-20]_.

mps/manual/source/design/index.rst

@@ -40,6 +40,7 @@ Design
     sp
     splay
     stack-scan
+    tests
     testthr
     thread-manager
     thread-safety

mps/manual/source/design/old.rst

@@ -43,5 +43,4 @@ Old design
     seg
     strategy
     telemetry
-    tests
     trace