Back out READ/WRITE_INTERLACING changes

Now that the code works consistently so that these just switch off the support
for having libpng do the interlace/deinterlace the old names make more sense,
restoring them avoids cruft in the configuration file and avoids an unnecessary
version specific change.

Signed-off-by: John Bowler <jbowler@acm.org>

contrib/libtests/readpng.c

@@ -31,13 +31,6 @@
 #  include "../../png.h"
 #endif
 
-#if PNG_LIBPNG_VER < 10700
-   /* READ_INTERLACING was used instead of READ_DEINTERLACE. */
-#  ifdef PNG_READ_INTERLACING_SUPPORTED
-#     define PNG_READ_DEINTERLACE_SUPPORTED
-#  endif
-#endif
-
 static int
 read_png(FILE *fp)
 {
@@ -77,12 +70,12 @@ read_png(FILE *fp)
 
       {
          png_uint_32 height = png_get_image_height(png_ptr, info_ptr);
-#        ifdef PNG_READ_DEINTERLACE_SUPPORTED
+#        ifdef PNG_READ_INTERLACING_SUPPORTED
             int passes = png_set_interlace_handling(png_ptr);
-#        else
+#        else /* !READ_INTERLACING */
             int passes = png_get_interlace_type(png_ptr, info_ptr) == 
                PNG_INTERLACE_ADAM7 ? PNG_INTERLACE_ADAM7_PASSES : 1;
-#        endif
+#        endif /* !READ_INTERLACING */
          int pass;
 
          png_start_read_image(png_ptr);
@@ -91,10 +84,10 @@ read_png(FILE *fp)
          {
             png_uint_32 y = height;
 
-#           ifndef PNG_READ_DEINTERLACE_SUPPORTED
+#           ifndef PNG_READ_INTERLACING_SUPPORTED
                if (passes == PNG_INTERLACE_ADAM7_PASSES)
                   y = PNG_PASS_ROWS(y, pass);
-#           endif
+#           endif /* READ_INTERLACING */
 
             /* NOTE: this trashes the row each time; interlace handling won't
              * work, but this avoids memory thrashing for speed testing.