[devel] PNG_EXPORT changed to include an 'ordinal' field

    for DEF file generation.

    PNG_CALLBACK added to make callback definitions uniform.  PNGAPI split
    into PNGCAPI (base C form), PNGAPI (exports) and PNGCBAPI (callbacks),
    and appropriate changes made to all files.  Cygwin builds re-hinged to
    allow procedure call standard changes and to remove the need for the DEF
    file (fixes build on Cygwin).

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Glenn R-P
diff --git a/pngwio.c b/pngwio.c
index 1d395b5..45a3cb0 100644
--- a/pngwio.c
+++ b/pngwio.c
@@ -1,7 +1,7 @@
 
 /* pngwio.c - functions for data output
  *
- * Last changed in libpng 1.5.0 [March 10, 2010]
+ * Last changed in libpng 1.5.0 [March 12, 2010]
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -45,7 +45,7 @@
  * than changing the library.
  */
 #ifndef USE_FAR_KEYWORD
-void PNGAPI
+void PNGCBAPI
 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
 {
    png_uint_32 check;
@@ -65,7 +65,7 @@
 #define NEAR_BUF_SIZE 1024
 #define MIN(a,b) (a <= b ? a : b)
 
-void PNGAPI
+void PNGCBAPI
 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
 {
    png_uint_32 check;
@@ -123,7 +123,7 @@
 }
 
 #  ifdef PNG_STDIO_SUPPORTED
-void PNGAPI
+void PNGCBAPI
 png_default_flush(png_structp png_ptr)
 {
    png_FILE_p io_ptr;