graphics/zgv: Patched SlackBuild.

Fixes build failure with libpng16 (-current).

graphics/zgv/zgv.SlackBuild

@@ -77,6 +77,9 @@ for i in $CWD/patches/*; do
   patch -p0 < $i
 done
 
+# Patch for libpng16 (-current) thanks to Debian
+patch -p1 < $CWD/zgv_5.9-2.patch
+
 make SLKCFLAGS="$SLKCFLAGS"
 make install DESTDIR=$PKG
 

graphics/zgv/zgv_5.9-2.patch

@@ -0,0 +1,28 @@
+--- zgv-5.9.orig/src/readpng.c
++++ zgv-5.9/src/readpng.c
+@@ -55,7 +55,6 @@
+ fclose(global_png_infile);
+ }
+ 
+-
+ void my_png_error(png_structp png_ptr,const char *message)
+ {
+ strncpy(jpeg_png_errmsg,message,JPEG_PNG_ERRMSG_SIZE-1);
+@@ -63,7 +62,7 @@
+ use_errmsg=1;
+ 
+ /* cleanup is done after jump back, so just do that now... */
+-longjmp(png_ptr->jmpbuf,1);
++longjmp(png_jmpbuf((png_ptr)),1);
+ }
+ 
+ 
+@@ -132,7 +131,7 @@
+   return(_PICERR_NOMEM);
+   }
+ 
+-if(setjmp(png_ptr->jmpbuf))
++  if (setjmp(png_jmpbuf((png_ptr))))
+   {
+   /* if we get here, there was an error. */
+   /* don't use local variables here, they may have been blasted */