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/proto/ex_getln.pro b/src/proto/ex_getln.pro
index 8095eff..5d51370 100644
--- a/src/proto/ex_getln.pro
+++ b/src/proto/ex_getln.pro
@@ -12,7 +12,7 @@
 int cmdline_overstrike(void);
 int cmdline_at_end(void);
 colnr_T cmdline_getvcol_cursor(void);
-void free_cmdline_buf(void);
+void free_arshape_buf(void);
 void putcmdline(int c, int shift);
 void unputcmdline(void);
 int put_on_cmdline(char_u *str, int len, int redraw);