Move running of vcprompt into own function
Fix bug when format string has a trailing '%'

The check for a trailing percent sign would not trigger, because it
checks for the character '0' instead of \0.
update contributor list
Check for wc.db first

This enables support for newer svn repositories which don't have a
.svn/entries file anymore
Simplify svn_get_info()'s error handling
Add test for missing ".svn/entries"