renameat/renameat01.c: cleanup

Add renameat.h to encapsulate renameat syscall.
Delete some useless comments.
Use some SAFE_* macros.
Move the test body from main() to renameat_verify().

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
Signed-off-by: Cyril Hrubis <metan@ucw.cz>
renameat/renameat01.c: add ELOOP, EROFS and EMLINK error value tests

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
Signed-off-by: Cyril Hrubis <metan@ucw.cz>