maxuploadsize should consider that post_max_size is the whole POST content

[Ruslan Kabalin]

In addition to respecting quota (), maxupload variable (which used to be in filebrowser pieform, now it is in get_max_upload_size function, see 7b2772a03 on master) considers minimum value of either 'post_max_size' or 'upload_max_filesize':

$maxuploadsize = min(get_real_size(ini_get('post_max_size')), get_real_size(ini_get('upload_max_filesize')));

It should be taken into account that post_max_size PHP setting evaluates the whole POST content (which includes file name and other from values, not only the file itself), thus assuming that file should be equal to this value while determining maxupload size is incorrect.