Update JSqlParserCC.jj

Add support for DB2 Updates with Select clause
Update Update.java

Add support for DB2 Updates with Select clause
Update JSqlParserCC.jj

For DB2 "$" is also a standard letter, so handle "$" as #LETTER.
Update Update.java

Add necessary Select import for Update with Select
Update UpdateTest.java

Add an SQL test for Update with Select
Merge pull request #78 from CeeKayGit/master

Add support for DB2 specials: Updates with Select clause & "$" as standard #LETTER.