debug: better computation of stride for ArrayType
debug: better computation of stride for ArrayType

If the DWARF attribute for the stride of an array in bits is not
present, fall back to the attribute that measures the stride in
bytes, and then to the size of the type of the array's elements.

Change-Id: Ied5afbba6bf05481731a115c8c22d46892330e60
Reviewed-on: https://go-review.googlesource.com/10249
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

golang/debug