patch 9.0.1403: unused variables and functions

Problem:    Unused variables and functions.
Solution:   Delete items and adjust #ifdefs. (Dominique Pellé, closes #12145)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index f945b38..e814431 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -3569,6 +3569,7 @@
     return FALSE;
 }
 
+#if defined(FEAT_EVAL) || defined(PROTO)
 /*
  * Return TRUE if "cmd" starts with "123->", a number followed by a method
  * call.
@@ -3580,6 +3581,7 @@
 
     return p > cmd && (p = skipwhite(p))[0] == '-' && p[1] == '>';
 }
+#endif
 
 /*
  * Find an Ex command by its name, either built-in or user.