fix reported array basicsize

this fixes object size calculation. The previous implementation
did not work in cases where the datatype stored in the tinyarray
is narrower than a machine word, and the compiler padded
'Array_base' to be word-aligned.
4 jobs for bugfix/windows in 55 seconds (queued for 4 minutes and 23 seconds)
Status Name Job ID Coverage
passed python2 #35410


passed python3 #35411


canceled python2 #35408

canceled python3 #35409