Add note about commit status API deprecation

[ci skip]

doc/api/commits.md

@@ -211,7 +211,12 @@ Example response:
 }
 ```
-## Get the status of a commit
+## Commit status
+
+Since GitLab 8.1, this is the new commit status API. The documentation in
+[ci/api/commits](../ci/api/commits.md) is deprecated.
+
+### Get the status of a commit
 Get the statuses of a commit in a project.
@@ -285,7 +290,7 @@ Example response:
 ]
 ```
-## Post the build status to a commit
+### Post the build status to a commit
 Adds or updates a build status of a commit.

doc/ci/api/commits.md

 # Commits API
+**DEPRECATED**
+
+Since GitLab 8.1, there is a new commit status API. Please see the [revised
+documentation](../../api/commits.md#commit-status).
+
+---
+
 __Authentication is done by GitLab CI project token__
 ## Commits