pwrite/pwrite02.c: cleanup

Merge pwrite02, pwrite03 into one pwrite02 test, which contains
ESPIPE, EINVAL, EBADF and EFAULT tests.

Remove useless comments and make use of SAFE_MACROS().

Delete some useless code and do some code re-arrangement.

printf() is not async-signal-safe, so use write(2) in signal handler
directly.

Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
pwrite/pwrite02.c: make EBADF error value tests sufficient

Adds test for pwrite() and read only fd.

Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>