[LTP] Add new test for pipe2 with/without O_NONBLOCK mode

[laniel_francis@privacyrequired.com]

I added a new test file (pipe2_03.c) to test pipe2 system call with and without
O_NONBLOCK enabled.
This test uses the macro SAFE_PIPE2 that I added, this macro is just the
equivalent of SAFE_PIPE for pipe2.

The diff --stat output is the following:
include/safe_macros_fn.h                   |   3 +++
include/tst_safe_macros.h                  |   3 +++
lib/safe_macros.c                          |  15 ++++++++++++++
testcases/kernel/syscalls/pipe2/.gitignore |   1 +
testcases/kernel/syscalls/pipe2/pipe2_03.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 152 insertions(+)


Best regards.