Fix py-pykde4 against newest clang

[adridg]

Summary

PyList_SET_ITEM() is supposed to be void, but as a macro it's an
expression and has a pointer value. Clang 4.0 trips on the bogus
pointer comparison; given the comparison, it should be PyList_SetItem()
which returns -1 on failure.

Test Plan

py-kde4 builds with these patches on -CURRENT with the clang4 branch.

[adridg]

Before Tobias reminds me that there should be an explanation of
why the patches are necessary ..

[tcberner]

Looks good.