NATIVE_FLOAT or NATIVE_DOUBLE types, all numbers are converted to strings and
passed through to ODPI-C in all Python versions; improved error message when
a value cannot be represented by an Oracle number value; improved test suite to
verify that calling executemany() with integers, floats and decimal values
intermixed with each other works as expected
(https://github.com/oracle/python-cx_Oracle/issues/241).
- use a prefix of cxo/CXO for all variables, methods and constants
- create common include file and use separate compilation units
- consolidate all transformations to/from Python objects
