Misc addendum to CORE-14271 (#1529)

Misc addendum to CORE-14271 (#1529)

* [ADVAPI32] Simplify RtlCreateUnicodeStringFromAsciiz() return value check

RtlCreateUnicodeStringFromAsciiz() returns a BOOLEAN, not a BOOL.

No functional change.

Addendum to
CORE-14271

* [USER32] Simplify RtlCreateUnicodeStringFromAsciiz() return value check

RtlCreateUnicodeStringFromAsciiz() returns a BOOLEAN, not a UINT.

Also, add a FIXME.

No functional change.

Addendum to
CORE-14271

* [USER32] Simplify RegisterClipboardFormatA/W() a bit

No functional change.

* [UDFS] Simplify SeSinglePrivilegeCheck() return value check

No functional change.

Addendum to
CORE-14271