Leading or trailing white space characters in file names

[Travis Cobbs]

That makes sense. How about the following wording as a replacement for what I said above:

Furthermore, filenames that contain leading or trailing white space characters cannot be referenced from other LDraw files, so they are discouraged.

In addition to the above, update the <file> specification for type 1 lines to be as follows (adding the second sentence):

<file> is the filename of the sub-file referenced and must be a valid LDraw filename. Any leading and trailing white space around the filename will be ignored.