Remove unnecessary use of non-portable 'mkdir()'

[Lubomir I. Ivanov]

On 15 February 2015 at 22:09, Lubomir I. Ivanov <neolit123 at gmail.com> wrote:
> i guess we can still keep the wrapper i wrote since - if my memory
> serves me correctly this is the second time(?) mkdir usage pops out.
>

yeah, so it wasn't in "master", but was in my "minizip" branch where i
wrote the same wrapper when adding the experimental code to replace
libzip.
(i.e. mkdir for creating folders when extracting from a zip)

lubomir
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