* fix linking of vector types when linking hipcc objects with gcc
* use __atribute__((vector_size)) with both clang and gcc
and reinstate nonaligned n=3 vector type
* use implicit conversion to value and ext_vector_type when available
* Alternate formulation for GCC compatibility
* Built-in arrays don't mix well with placement new
* Fix typo
* Add conversions to enum
* Fix Scalar_accessor assignment.
* Update hip_vector_types.h
* stir up the underlying_type hideous mess
This fixes the HIP build issue "error: only enumeration types have underlying types".
jglaser
00d735cdc9