Build issue with (non-turbo) libjpeg < 9d related to plugins/encoder_jpeg.cc

[jerstlouis]

Builds using jpeg-9a,b,c are failing due to type mismatch invoking jpeg_mem_dest().

Like libjpeg-turbo, the prototypes in non-turbo libjpeg up to jpeg-9c used unsigned long (while LIBJPEG_TURBO_VERSION is not defined):

EXTERN(void) jpeg_mem_dest JPP((j_compress_ptr cinfo,
			       unsigned char ** outbuffer,
			       unsigned long * outsize));

The code in encoder_jpeg.cc declares the output size as:

#ifdef LIBJPEG_TURBO_VERSION
  unsigned long outlength = 0;
#else
  size_t outlength = 0;
#endif

so this should probably be something like:

#if defined(LIBJPEG_TURBO_VERSION) || (JPEG_LIB_VERSION_MAJOR < 9 || (JPEG_LIB_VERSION_MAJOR == 9 && JPEG_LIB_VERSION_MINOR < 4))
  unsigned long outlength = 0;
#else
  size_t outlength = 0;
#endif