Make zstdcat to follow symbolic links

[vejnar]

Since #1520 has been merged, commands like zstdcat properly detect symbolic links on Linux. But the consequence is that they output nothing when executed on a symbolic link. According to the manual, zstdcat includes -f, which should follow symbolic links. This is also how most *cat commands like zcat behave.

Please comment and I would be glad if you could consider this request for merging into master. Thanks.
Charles

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[terrelln]

Thanks for the patch!

Note for others that see this issue, until the next zstd release this can be worked around by using with zstdcat -f.

[terrelln]

Oh, nearly forgot! Would you mind adding a test to tests/playTests.sh that makes sure it works zstdcat works with symlinks? There is already a section that tests zstdcat, so you can just append a test there.

If you don't have the time, let me know and I can add the test myself. If I don't hear back in a few days I'll go ahead and merge and add the test.