patch 9.1.0633: Compilation warnings with `-Wunused-parameter`

Problem:  Compilation warnings with `-Wunused-parameter`
Solution: Add the `UNUSED` macro where needed, and remove some
          superfluous ones (Dominique Pellé)

Change fixes these kind of warnings when building without the channel
feature:

```
eval.c:6122:15: warning: unused parameter ‘tv’ [-Wunused-parameter]
     typval_T *tv,
               ^
eval.c:6123:14: warning: unused parameter ‘tofree’ [-Wunused-parameter]
     char_u **tofree,
              ^
eval.c:6124:13: warning: unused parameter ‘numbuf’ [-Wunused-parameter]
     char_u *numbuf,
             ^
eval.c:6125:10: warning: unused parameter ‘composite_val’ [-Wunused-parameter]
     int  composite_val)
```

closes: #15378

Signed-off-by: Dominique Pellé <dominique.pelle@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 398b482..373cd8c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    633,
+/**/
     632,
 /**/
     631,