ntdll/tests: Only test the readcount for a read below 0x10000 if  the return code indicates a partial copy result.

The scan codes for the numeric keypad keys and those for the arrow keys and
keys like Home, End, etc. often match (ignoring the extended key bit).
However, if you map from one of those scan codes to a vkey, Windows reliably
prefers the non-numpad vkey.

Based on a patch by Louis Lenders.

Based on a patch by Louis Lenders.