Merge pull request #6 from alexlib/image_processing

Image processing
Changed call of header files compatible to mvs2010
added free(buf2) in imageprocessing.c
modified alex_lowpass_3 --> as we use pointers, we should stay in the memory and do not uses adresses out of the image domain. Removed the shift in writing the data to img_lp
added subtract_img8Bit to provide first set image arithmetics
Merge pull request #3 from psteinhoff/image_processing

Image processing