patch 9.0.0634: evaluating "expr" options has more overhead than needed

Problem:    Evaluating "expr" options has more overhead than needed.
Solution:   Use call_simple_func() for 'foldtext', 'includeexpr', 'printexpr',
            "expr" of 'spellsuggest', 'diffexpr', 'patchexpr', 'balloonexpr',
            'formatexpr', 'indentexpr' and 'charconvert'.
diff --git a/src/findfile.c b/src/findfile.c
index 5751a07..9ce733c 100644
--- a/src/findfile.c
+++ b/src/findfile.c
@@ -2002,7 +2002,8 @@
     current_sctx = curbuf->b_p_script_ctx[BV_INEX];
 
     res = eval_to_string_safe(curbuf->b_p_inex,
-		 was_set_insecurely((char_u *)"includeexpr", OPT_LOCAL), TRUE);
+	    was_set_insecurely((char_u *)"includeexpr", OPT_LOCAL),
+								   TRUE, TRUE);
 
     set_vim_var_string(VV_FNAME, NULL, 0);
     current_sctx = save_sctx;