improve MySqlParameterizedOutputVisitor
improve sqlwall and parser
support sql ast object toString
Merge remote-tracking branch 'upstream/master'
Merge pull request #686 from wenshao/master

StatementImpl增加dbType使得toString是能够选择不同的visitor
ameterizedOutputVisitorTest_6.java
Merge pull request #687 from yakolee/master

improve sqlwall and parser
bug fixed for sql parser
Merge pull request #688 from wenshao/master

bug fixed for sql parser
add license
Merge pull request #689 from yakolee/master

add license
support doubleQuote
Merge remote-tracking branch 'upstream/master'
Merge pull request #690 from wenshao/master

支持doubleQuote
improve sqlwall
Merge pull request #691 from yakolee/master

improve sqlwall
bugfix for sqlparser
improve pg sql parser
Merge pull request #695 from wenshao/master

improve pg sql parser
Merge pull request #696 from yakolee/master

bugfix for sqlparser