Eliminate some compiler warnings * Makefile.am (AM_CXXFLAGS): Build with -W -Wall by default. * __py_struct_from_dict__.cc (F__py_int64_scalar_value__, F__py_uint64_scalar_value__, F__py_is_none__, F__py_isinstance__, F__py_objstore_del__, F__py_objstore_get__, F__py_objstore_put__, F__py_string_value__, F__py_struct_from_dict__): Remove unused parameter to eliminate -Wunused-parameter warning. * pyexec.cc (Fpyexec): Likewise. * oct-py-init.cc (pytave::py_init): Declare argv array correctly to eliminate -Wwrite-strings warning. * oct-py-types.cc (pytave::make_py_bool): Explicitly increment and return value to eliminate -Wstrict-aliasing warning. (pytave::make_py_complex, pytave::extract_py_complex): Copy complex values between C++ and Python types to eliminate -Wstrict-aliasing warning. (pytave::extract_py_int64): Add braces to nested if block to eliminate -Wparentheses warning.