change string([]byte) to pass array, rather than &a[0],

change string([]byte) to pass array, rather than &a[0],
to string convert.  if the byte array has length 0,
the computation of &a[0] throws an index bounds error.

for fixed size arrays, this ends up invoking arrays2d
unnecessarily, but it works.

R=ken
DELTA=304  (44 added, 28 deleted, 232 changed)
OCL=15674
CL=15678