[YAML] added backtick to the list of characters that trigger quotes as it is reserved for future use (patch from indeyets)
[YAML] added backtick to the list of characters that trigger quotes as it is reserved for future use (patch from indeyets)

git-svn-id: eb40f308bf1d815258b979d032d59e01989ca262@28201 ee427ae8-e902-0410-961c-c3ed070cd9f9

fabpot-graveyard/yaml,aredridel/symfony1-yaml