[patch] png2theora fails to compile with libpng 1.6 and above

There is no more png_sizeof in libpng 1.6

examples/png2theora.c uses png_sizeof but it also has #include <string.h> so the attached patch simply replaces usages of png_sizeof with sizeof Seems to work fine here

Original bug report was filed here:

https://bugs.gentoo.org/show_bug.cgi?id=465450

The errors look like this:

libtool: link: x86_64-pc-linux-gnu-gcc -I/usr/include/libpng16 -Wall -Wno-parentheses -march=native -O2 -pipe -Wl,-O1 -o .libs/png2theora png2theora-png2theora.o -Wl,--as-needed ../lib/.libs/libtheoraenc.so ../lib/.libs/libtheoradec.so -logg -lpng16 -lm png2theora-png2theora.o: In function png_read': png2theora.c:(.text+0x1bf): undefined reference to png_sizeof' png2theora.c:(.text+0x1e7): undefined reference to `png_sizeof' collect2: error: ld returned 1 exit status make[2]: *** [png2theora] Error 1