Fix bug computing hblocks and vblocks with libjpeg.
Fix bug computing hblocks and vblocks with libjpeg.

The width_in_blocks and height_in_blocks fields in jpeg_decompress_struct
 do not include any padded blocks inside the MCU (those that are known to
 be all zero by the decoder) and this is corrected by manually computing
 the correct values.
This is necessary because image_init() uses the hblock and vblock fields
 of the jpeg_component struct to allocate space to store the DCT
 coefficients for all jpeg decoders supported.

negge/jpeg_gpu,negge/jpeg_gpu