[libpng17] Enable parallel tests and rearrange TESTS order to take advantage of

the massive speed improvements use a make capable of parallel builds
on a multi-CPU machine and pass the right arguments to make (-j10000
for GNU make) to get the build to run in parallel.

tests/pngstest-6a08

@@ -0,0 +1,23 @@
+#!/bin/sh
+#
+# The name of the script should be:
+#
+#  pngstest-....
+#
+# Where the last four characters are the suffix of a PNGSuite test file, or
+# -error, in which case the x files are used.
+case "$0" in
+   */pngstest-????)
+      suffix="${0##*/pngstest\-}"
+      exec ./pngstest --tmpfile "error" "${srcdir}/contrib/pngsuite/"[^x]*"${suffix}.png";;
+
+   */pngstest-error)
+      # Test files may not exist, fake a failure if not
+      set "${srcdir}/contrib/pngsuite/"x*"${suffix}.png"
+      if test $# -ne 1 -o $1 != "${srcdir}/contrib/pngsuite/x*${suffix}.png"
+      then
+         exec ./pngstest --tmpfile "${suffix}" "${srcdir}/contrib/pngsuite/"x*"${suffix}.png"
+      else
+         exit 1
+      fi;;
+esac