This patch was required for me to compile XV with libjpeg 6.0, and
while it isn't needed to use the PNG patch, you may find it help-
ful.

Andreas Dilger <adilger@enel.ucalgary.ca>
http://www-mddsp.enel.ucalgary.ca/People/adilger/

*** xv-3.10a.orig/xvjpeg.c	Thu Jan  5 01:17:13 1995
--- xv-3.10a/xvjpeg.c	Wed May 29 11:15:02 1996
***************
*** 51,61 ****
  static    void         clickJD            PARM((int, int));
  static    void         doCmd              PARM((int));
  static    void         writeJPEG          PARM((void));
! METHODDEF void         xv_error_exit      PARM((j_common_ptr));
! METHODDEF void         xv_error_output    PARM((j_common_ptr));
! METHODDEF void         xv_prog_meter      PARM((j_common_ptr));
  static    unsigned int j_getc             PARM((j_decompress_ptr));
! METHODDEF boolean      xv_process_comment PARM((j_decompress_ptr));
  static    int          writeJFIF          PARM((FILE *, byte *, int,int,int));
  
  
--- 51,61 ----
  static    void         clickJD            PARM((int, int));
  static    void         doCmd              PARM((int));
  static    void         writeJPEG          PARM((void));
! METHODDEF(void)        xv_error_exit      PARM((j_common_ptr));
! METHODDEF(void)        xv_error_output    PARM((j_common_ptr));
! METHODDEF(void)        xv_prog_meter      PARM((j_common_ptr));
  static    unsigned int j_getc             PARM((j_decompress_ptr));
! METHODDEF(boolean)     xv_process_comment PARM((j_decompress_ptr));
  static    int          writeJFIF          PARM((FILE *, byte *, int,int,int));
  
  
***************
*** 400,406 ****
  
  
  /**************************************************/
! METHODDEF void xv_error_exit(cinfo) 
       j_common_ptr cinfo;
  {
    my_error_ptr myerr;
--- 398,404 ----
  
  
  /**************************************************/
! METHODDEF (void) xv_error_exit(cinfo) 
       j_common_ptr cinfo;
  {
    my_error_ptr myerr;
***************
*** 412,418 ****
  
  
  /**************************************************/
! METHODDEF void xv_error_output(cinfo) 
       j_common_ptr cinfo;
  {
    my_error_ptr myerr;
--- 410,416 ----
  
  
  /**************************************************/
! METHODDEF (void) xv_error_output(cinfo) 
       j_common_ptr cinfo;
  {
    my_error_ptr myerr;
***************
*** 426,432 ****
  
  
  /**************************************************/
! METHODDEF void xv_prog_meter(cinfo)
       j_common_ptr cinfo;
  {
    struct jpeg_progress_mgr *prog;
--- 424,430 ----
  
  
  /**************************************************/
! METHODDEF (void) xv_prog_meter(cinfo)
       j_common_ptr cinfo;
  {
    struct jpeg_progress_mgr *prog;
***************
*** 671,677 ****
  
  
  /**************************************************/
! METHODDEF boolean xv_process_comment(cinfo)
       j_decompress_ptr cinfo;
  {
    int          length, hasnull;
--- 669,675 ----
  
  
  /**************************************************/
! METHODDEF (boolean) xv_process_comment(cinfo)
       j_decompress_ptr cinfo;
  {
    int          length, hasnull;