[libpng15] Corrected Android builds and corrected libpng.vers with symbol

prefixing This adds an API to set optimization options externally,
    providing an alternative and general solution for the non-portable
    run-time tests used by the ARM Neon code.  It also makes those tests
    compile and link on Android.
  The order of settings vs options in pnglibconf.h is reversed to allow
    settings to depend on options and options can now set (or override) the
    defaults for settings.

pngstruct.h

@@ -355,5 +355,10 @@ struct png_struct_def
 /* New member added in libpng-1.5.7 */
    void (*read_filter[PNG_FILTER_VALUE_LAST-1])(png_row_infop row_info,
       png_bytep row, png_const_bytep prev_row);
+
+   /* Options */
+#ifdef PNG_SET_OPTION_SUPPORTED
+   png_byte options;           /* On/off state (up to 4 options) */
+#endif
 };
 #endif /* PNGSTRUCT_H */