[FIX] fileUrlToString-ls ( [er][et][sm][cd] Works on Win XP Pro; Recommend including. )

[tomkoenig at mindspring.com]

I think this coding is also easier to read.
Tested with 3.7a #5623
| dir file |
dir := ServerDirectory new fullPath: (FileDirectory default url).
file := dir asServerFileNamed: 'test.txt'.
Transcript show: (file fileNameRelativeTo: dir); cr.
Is broken w/o fix
/C:\Documents and Settings\Tom Koenig\Desktop\Squeak3.7\test.txt
and is fixed with fix
C:\Documents and Settings\Tom Koenig\Desktop\Squeak3.7\test.txt