1. New methods of TSQLServer class (also for Oracle, MySQL, ODBC):
     Exec() - execute query which does not produce any result
     GetTablesList() - return list of tables names in data-base independent form
     IsTableExists() - check if table of given name exists
     GetTableInfo() - returns instance of TSQLTableInfo with list of columns.
2. New methods of TSQLStatement class (also for Oracle, MySQL, ODBC):
     IsNull() - checks, if field value is NULL
     SetNull() - sets parameter value to NULL


New TSQLTableInfo contains information about table and table columns.
For MySQL additional information like engine type, creation and last update time is provided


New TSQLColumnInfo class contains information about single column from SQL table
Has following methods:
   GetTypeName() - field type name in string form as it is reported by correspondent
          database method. Some databases providing full type name like "numeric(20)",
          other showing only "NUMERIC". As a result, one cannot use this string directly
          to create new field of similar types in other table
   IsNullable() - says if field value can be NULL or not
   GetSQLType() - returns kind of sql type. Possible values:
      TSQLServer::kSQL_NONE        data type unknown
      TSQLServer::kSQL_CHAR        CHAR(n) - string with fixed length n
      TSQLServer::kSQL_VARCHAR     VARCHAR(n) - string with variable length upto n
      TSQLServer::kSQL_INTEGER     INTEGER, INT, TINYINT - any integer types
      TSQLServer::kSQL_FLOAT       FLOAT - float value
      TSQLServer::kSQL_DOUBLE      DOUBLE - double precision value
      TSQLServer::kSQL_NUMERIC     NUMERIC(n,s), NUMBER(n,s) - numeric values with length and precion
      TSQLServer::kSQL_BINARY      BLOB, VARBINARY  - binary data (vriable or fixed size)
      TSQLServer::kSQL_TIMESTAMP   TIMESTAMP - time and date stamp
   GetSize() - size of field in database. -1 if not known.
   GetLength() - length argument in type declaration like CHAR(len) or NUMERIC(len), -1 if not defined
   GetScale() - second argument in declarations like NUMERIC(len, s), -1 if not defined
   GetSigned() - is type signed(==1) or unsigned(==0), -1 if not defined


git-svn-id: http://root.cern.ch/svn/root/trunk@15305 27541ba8-7e3a-0410-8455-c3a389f83636