[PATCH-for-5.1] .travis.yml: Deprecate it in favor of GitLab CI

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

As of QEMU 5.2 we prefer to focus our CI development on GitLab.
Mark Travis-CI as deprecated (adding a big warning).

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 docs/system/deprecated.rst | 11 +++++++++++
 .travis.yml                |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 851dbdeb8a..c17a5b0896 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -17,6 +17,17 @@ they were first deprecated in the 2.10.0 release.
 What follows is a list of all features currently marked as
 deprecated.
 
+Build and test automation
+-------------------------
+
+``Travis-CI`` (Since 5.2)
+'''''''''''''''''''''''''
+
+``Travis-CI`` is deprecated in favor of GitLab-CI.
+
+The '.travis.yml' configuration should only be modified to remove jobs
+when equivalent exist on GitLab-CI. Adding new jobs is not allowed.
+
 System emulator command line arguments
 --------------------------------------
 
diff --git a/.travis.yml b/.travis.yml
index 6695c0620f..4ad243f511 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,3 +1,10 @@
+#  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING
+#
+#  As of QEMU 5.2, this file is now deprecated in favor of GitLab CI.
+#  Do not modify, except to remove jobs ported to GitLab CI.
+#
+#  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING
+
 # The current Travis default is a VM based 16.04 Xenial on GCE
 # Additional builds with specific requirements for a full VM need to
 # be added as additional matrix: entries later on
-- 
2.21.3