(memoryviews don't support complex structures right now)

This should fix the test_py3kwarn failure on OS X.  test_support.import_module
also requires this.

Based on a patch by Meador Inge.

 - rename to _test_structmembersType to avoid the class being automatically
   called by test_capi

 - allow space for trailing NUL in inplace_member field of all_structmembers

 - use T_STRING_INPLACE instead of T_INPLACE_STRING as keyword argument
   to _test_structmembersType initializer

 - don't attempt to initialize inplace_member field if T_STRING_INPLACE
   argument wasn't supplied.

 * 'z', 'z#', 'z*' does also accept Unicode
 * unify types name: replace "string or Unicode objet" by "string or Unicode"

Improve clear() method.  Keeps key/value refcnts >= 1 until final dict.clear() so that decrefs to zero won't trigger arbitrary code .  Also runs a bit faster.

NotImplementedError on Windows XP and below.

also normalize how this error is checked