creat, mkdir: bugfix in umask handling, make umask optional
creat, mkdir: bugfix in umask handling, make umask optional

libsmbclient expects a mode_t parameter, which is an integer bitmask,
not a string. Fix this bug.

Make the mode parameters optional for the caller, fall back on 0777
masks for the default case.

aklomp/libsmbclient-php,aklomp/libsmbclient-php,aklomp/libsmbclient-php