Support full SQL TYPE IS syntax

[fm-117]

Following #2186.

The goal here is to extend the parser to support full syntax for special usage SQL TYPE IS. See https://www.ibm.com/docs/en/db2-for-zos/12?topic=cobol-host-variables-in.

New required contextual keywords:

• RESULT-SET-LOCATOR
• LIKE
• AS
• LOCATOR
• ROWID
• LARGE
• BLOB
• CHAR
• CLOB
• DBCLOB
• BLOB-LOCATOR
• CLOB-LOCATOR
• DBCLOB-LOCATOR
• BLOB-FILE
• CLOB-FILE
• DBCLOB-FILE
• K
• M
• G

ANTLR grammar:

sqlTypeClause:
  SQL TYPE IS (binaryVariable | (resultSetLocator VARYING) | tableLocator | lobVariableOrLocatorOrFile | xmlVariableOrFile | rowid);

binaryVariable:
  already defined by #2186 
tableLocator:
  TABLE like tableName=UserDefinedWord as locator;
lobVariableOrLocatorOrFile:
  lobVariable | lobLocator | lobFile;
xmlVariableOrFile:
  XML as (lobVariable | lobFile);

lobVariable: ((BINARY large OBJECT | blob) | (CHARACTER large OBJECT | char large OBJECT | clob) | dbclob) LeftParenthesisSeparator length=IntegerLiteral lobVariableUnit? RightParenthesisSeparator;
lobVariableUnit: k | m | g;
lobLocator: blobLocator | clobLocator | dbclobLocator;
lobFile: blobFile | clobFile | dbclobFile;