patch 8.1.1632: build with EXITFREE but without +arabic fails

Problem:    Build with EXITFREE but without +arabic fails.
Solution:   Rename the function and adjust #ifdefs. (closes #4613)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 303786c..c9c63ac 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -3174,7 +3174,7 @@
 
 # if defined(EXITFREE) || defined(PROTO)
     void
-free_cmdline_buf(void)
+free_arshape_buf(void)
 {
     vim_free(arshape_buf);
 }