[Beignet] [PATCH 0/6 OpenCL-1.2] Implement the printf feature for CL

[junyan.he at inbox.com]

From: Junyan He <junyan.he at linux.intel.com>

Because OCL spec indicates that the format of prinf is const and always
available in compiling time. So we just prepare two buffers to collect
the output data and output index of the GPU. Then we print out the data
using the stdc printf.

TODO:
1. Just support %d and %i now, other format will be implemented soon later.
2. Do not support flags and signs of format now, also will be implemented later.

Signed-off-by: Junyan He <junyan.he at linux.intel.com>