-this means you have compiled another module that includes setjmp.h,
-which is hazardous because the two modules might not include exactly
-the same setjmp.h. If you are sure that you know what you are doing
-and that they are exactly the same, then you can comment out or
-delete the two lines. Better yet, use the cexcept interface
-instead, as demonstrated in contrib/visupng of the libpng distribution.
+The ./configure script should work compatibly with what scripts/makefile.*
+did, however there are some options you might need to add to configure
+explicitly, which previously was done semi-automatically (if you didn't edit
+scripts/makefile.* yourself, that is)
+
+CFLAGS="-Wall -O -funroll-loops \
+-malign-loops=2 -malign-functions=2" ./configure --prefix=/usr/include \
+--with-pkgconfigdir=/usr/lib/pkgconfig --includedir=/usr/include
+
+You can alternatively specify --includedir=/usr/include, /usr/local/include,
+/usr/include/libpng%NN%, or whatever.
+
+If you find that the configure script is out-of-date or is not supporting
+your platform properly, try running autogen.sh to regenerate "configure",
+"Makefile.in", and the other configuration files. Then try configure again.