Call PyErr_BadInternalCall() if inputs are not unicode strings.

 * Replace PyUnicode_AS_UNICODE by PyUnicode_AsUnicode, PyUnicode_AS_UNICODE is
   no more a real macro
 * Replace Py_UNICODE by wchar_t in code specific to Windows

 * Use Py_UCS4* buffer instead of Py_UNICODE*
 * Use "I" or "L" format, instead of "u" format

Jarosch.

Jarosch.

 * Change its prototype: PyObject* instead of PyUnicodeoObject*.
 * Remove an old assertion, the result of PyUnicode_READY (_PyUnicode_Ready)
   must be checked instead

Move these macros to unicodeobject.c

Cleanup also the code (avoid the goto).

To make it clearer that Py_BUILD_ASSERT_EXPR(cond) cannot be used as
assert(cond).

 * Downcasting from Py_UCS4 to Py_UNICODE is wrong is Py_UNICODE is 16-bit
   wchar_t
 * Remove old special case in getstring(), unicode is now handled separetely

Move other various macros to pymcacro.h

Thanks Rusty Russell for having written these amazing C macros!

formatbuf is now an array of Py_UCS4, not of Py_UNICODE