Backport two Objective-C bug fixes (D18672)

Add patches for head rS342592 and rS342593 (D18691)

Add patch files for head rS342592 and rS342593, which correspond to the
following upstream revisions:

https://reviews.llvm.org/rL342397
https://reviews.llvm.org/rL342397

These fix an 'Assertion failed: ((VT.getVectorNumElements() +
N2C->getZExtValue() <= N1.getValueType().getVectorNumElements()) &&
"Extract subvector overflow!"), function getNode' when building the
multimedia/aom port (with AVX2 enabled).

PR: 234480
Submitted by: theraven, dim
Differential Revision: https://reviews.freebsd.org/D18672
Differential Revision: https://reviews.freebsd.org/D18691