Add partial data iteration

Add an iterator that will iterate over the result data of a query. The
missing part is to actually get the data from unixODBC into the Record
class.

Add the low level functions to get information from the columns. To get
data from unixODBC it's necessary to find out which column has which
data type, column name, size, etc.

UnixOdbcLL:

- Add ColumnDescriptor (enum for SQLColAttribute)
- Add SQLFetch
- Add SQLColAttribute

UnixOdbc:

- Add Record class (only a stub for now)
- Add RecordIterator class (iterate over fetch ())