Make idoublePrecision a true constant

Some older compilers might complain about
idoublePrecision not being a constant when
referenced inside the array declaration.
Silence warning about unused PyIntToINTXX

Make the declaration of PyIntToINT32/PyIntToINT64
conditional; otherwise the compiler always warns
about one of them being unused.
Remove unused function ClearError()
Merge pull request #108 from romuloceccon/remove_unused_ClearError

Remove unused function ClearError()
Merge pull request #106 from romuloceccon/constantize_invariable_value

Make idoublePrecision a true constant
Merge pull request #107 from romuloceccon/silence_unused_PyIntToINTXX_warning

Silence warning about unused PyIntToINTXX
merge from upstream
use 3-part version string