Fix Bug 757: Regression of URL to URI conversion (Encoded path not compatible w/ file scheme.

Regression of (Bug 683, Commit b98825eb7cfb61aead4a7dff57471cd2d2c26823).

The URI encoded path cannot be read by File I/O (if file scheme), since the latter
requests an UTF8/16 name, not an URI encoded name (i.e. %20 for space).

The encoded URL is produced if calling 'uri.toURL()' and hence
the new 'IOUtil.toURL(URI)' provides a custom conversion recovering the UTF name via 'new File(uri).getPath()'.

Tested w/
  - synthetic URI/URL coposition (unit test)
  - manual w/ moving 'build' to 'build öä lala' for gluegen, joal and jogl.

+++

Misc.:

- 'URI JarUtil.getURIDirname(URI)'  -> 'URI IOUtil.getDirname(URI)'

++