bcc kernel fusion: Fixed checks and added better error messages

b/21949580

Need to increment the slot iterator only after checking if the slot
is first in batch.

Succeeding kernel input data type has to strictly match the return
type of the preceding kernel.

Give error messages on all error exits, with better messages.

Change-Id: Icc50b85377e820333b13e57389e53363d4a7e89f
(cherry picked from commit 531d08c85971e47f58aedc093fbe83f1b909703e)
1 file changed