winemenubuilder: EnumResourceNamesW() returns false when we find the icon. So fix the corresponding misfiring trace.

shell32: A lot of lnk files have extra data blocks at the end, although they don't seem to matter much. So drop the corresponding ERR() to a WARN().

kernel32/tests: Despite the MSDN claims, GetComputerName() does not return the required buffer size... except on Vista. So update the tests accordingly.

Document the observed ExpandEnvironmentStrings() behavior.

advapi32: RegGetValue() should not return an error when expanding a string and given a NULL buffer and a zero size.

Adjust the tests to cover this case for REG_EXPAND_SZ registry
values. Improve the documentation a bit.