new faster SVN plugin

Faster alternative to the current SVN plugin implementation.

It sould work with svn 1.6, 1.7, 1.8.
Use `svn_prompt_info` method to enquire the svn data.
It's faster because his efficient use of svn (single svn call) done in the `parse_svn` function
Also changed prompt suffix *after* the svn dirty marker
Reports the svn upgrade error

*** IMPORTANT *** DO NO USE with the simple svn plugin, this plugin acts as a replacement of it.