Fix #35270: files with numbers higher than 2147483648 or with different numbers
of leading zeros but otherwise the same would show in random order in the file
browser. Selecting an item would change the order of all the items.

Problem was that it was comparing by parsing the number into an int, which has
only limited precision and does not care about the number of leading zeros. Now
do the comparison directly on the string.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56662 954f8c5b-7b00-dc11-b283-0030488c597c