[PATCH] Documentation/sphinx: fix primary_domain configuration

[John Keeping]

With Sphinx 1.5.3 I get the warning:

	WARNING: primary_domain 'C' not found, ignored.

It seems that domain names in Sphinx are case-sensitive and for the C
domain the name must be lower case.

Signed-off-by: John Keeping <john@xxxxxxxxxxxx>
---
 Documentation/conf.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/conf.py b/Documentation/conf.py
index f6823cf01275..7fadb3b83293 100644
--- a/Documentation/conf.py
+++ b/Documentation/conf.py
@@ -135,7 +135,7 @@ pygments_style = 'sphinx'
 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False
 
-primary_domain = 'C'
+primary_domain = 'c'
 highlight_language = 'none'
 
 # -- Options for HTML output ----------------------------------------------
-- 
2.12.0.377.gf910686b23.dirty