pdo: quote identifier for mysql

--HG--
branch : 0.9
bugfix (2ced049a962e)

--HG--
branch : 0.9
removed unused and stupid sly_Util_String::escapePHP() method (if you use this, you're probably doing something wrong)

--HG--
branch : 0.9
extra : rebase_source : d23321c8d68f7ca0b30f3f0e976710a6a6755d82