patch 8.2.2020: some compilers do not like the "namespace" argument

Problem:    Some compilers do not like the "namespace" argument.
Solution:   Rename to "use_namespace". (closes #7332)
diff --git a/src/version.c b/src/version.c
index 70ebd9c..4fdc0f1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2020,
+/**/
     2019,
 /**/
     2018,