Use "/" instead of "\\" as suffix when building URI from current directory.

This fixes test unit Read_ofx_content_53 under mono, which doesn't recognize the backslash at the end of the URI and then constructs the wrong path for the DTD look up when it appends its name as a relative path.
Merge pull request #9 from bjorg/master

Fix for Read_ofx_content_53 unit test under mono.