[C99] Claim conformance to "remove deprecation of aliased array parameters"

I can't locate a document number for this particular change, but C89
had the following entry in Future Language Directions:

The use of two parameters declared with an array type (prior to their
adjustment to pointer type) in separate lvalues to designate the same
object is an obsolescent feature.

C99 removed this entry. Clang and LLVM have never done anything in
support of that deprecation, so we trivially conform to its removal.