add pidfd_getfd and openat2 syscall numbers from linux v5.6
tree2ef58a104ff7da374e30042a243cfe15f9dff248
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-rw-r--r-- 6204 COPYRIGHT
-rw-r--r-- 6742 INSTALL
-rw-r--r-- 7515 Makefile
-rw-r--r-- 1028 README
-rw-r--r-- 6 VERSION
-rw-r--r-- 86797 WHATSNEW
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