Description:
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please add to the documentation for strftime(), that for unsupported conversion specifiers, the conversion might fail completely and return an empty string. 

on linux:
echo "x" . strftime("%m %C") . "x";
> "xNovember 09x"

on windows:
echo "x" . strftime("%m %C") . "x";
> "xx"
and NOT as expected "xNovember x" with just the second conversion missing.

ideally, the conversion specifier list could list if it's available on a specific platform. for people porting code from win to linux, this is a cruicial issue...

thanks & keep up the great work!







Reproduce code:
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From manual page: function.strftime#Description
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see description

Expected result:
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see description