Packed vector instruction arrays are causing crashes

[uxmal]

Reko's type inference is having an indigestion on SSE packed vector types (e.g. @rfalke 's https://github.com/rfalke/decompiler-subjects/tree/master/from_holdec/nim/x64_elf/subject.exe in #959) The type inference engine is making an assumptions that array expressions are always the result of dereferencing a pointer and simultaenously indexing it, but this is not the case with the way SSE instructions are rewritten to RTL.