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"
Merge branch 'svn-1.8-entries'

* svn-1.8-entries:
  Add test for missing ".svn/entries"
  Simplify svn_get_info()'s error handling
  Check for wc.db first

Conflicts:
	src/svn.c