Add O_TMPFILE to Fcntl?

[eserte]

Fcntl is currently lacking O_TMPFILE which is available in recent Linux versions (3.11 and newer, possibly backported to some 3.10 e.g. CentOS 7). O_TMPFILE could be useful to implement temporary files which are guaranteed to be cleaned up after process exit (something which is not true for temporary files created by File::Temp). Currently one needs to use a CPAN module (e.g. Linux::TempFile) to make use of it, or use somehow h2ph, or hardcode the constant value.

Maybe it could also be systematically checked if there are other useful constants from fcntl.h which could be added to Fcntl.