unsigned char * -> uint8_t *, more careful error handling
add variables for logging
-	change (unsigned char *) -> (uint8_t *)
-	add new logging function
-	change struct framebuffer.bpp -> struct framebuffer.bytes_per_pixel
-	rewrite draw_image()
-	change (unsigned char *) -> (uint8_t *)
-	rewrite error function of libpng/libjpeg
-	add new logging function
-	add new member struct image.current_frame (for yaimgfb)
add new logging function
add new logging function
add new logging function, use log file for logging
add include file, add variables for logging
add logging function, rewrite w3m_draw()