tests: enhance -k test

Add two more function calls to the stack.  Suggested by Masatake YAMATO.

* tests/stack-fcall.c (f1): Rename to f3.
(f1, f2): New functions.
* tests/strace-k.test: Update.
diff --git a/tests/strace-k.test b/tests/strace-k.test
index 3845c8c..f757fb9 100755
--- a/tests/strace-k.test
+++ b/tests/strace-k.test
@@ -23,7 +23,7 @@
 	fail_ "$STRACE $args failed"
 }
 
-expected='getpid f1 f0 main '
+expected='getpid f3 f2 f1 f0 main '
 result=$(sed -n '1,/(main+0x[a-f0-9]\+) .*/ s/^.*(\([^+]\+\)+0x[a-f0-9]\+) .*/\1/p' $LOG |
 	tr '\n' ' ')