Remove rounding, truncation is always correct.
Bind texture before querying width/height
Emit correct texture loads for ImageParam.

Also clean up the code a little bit
Print buffer_t contents when something in DEBUG mode
Bring OpenGL test up to date and clean them up
Initialize .host field for buffers created using create_buffer_t intrinsic.
create_buffer_t: initialize elem_size
Started small set of tests for OpenGL backend
Remove debug output