vsi_mkdir() creates a new directory with the indicated mode.
For POSIX-style systems, the mode is modified by the file creation mask
(umask). However, some file systems and platforms may not use umask, or
they may ignore the mode completely. So a reasonable cross-platform
default mode value is 0755.
With recursive = TRUE, creates a directory and all its ancestors.
This function is a wrapper for VSIMkdir() and VSIMkdirRecursive() in
the GDAL Common Portability Library.