[master] Bump version to 1.2.4beta04

pngtest.c

@@ -1689,4 +1689,4 @@ main(int argc, char *argv[])
 }
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef version_1_2_41beta03 your_png_h_is_not_version_1_2_41beta03;
+typedef version_1_2_41beta04 your_png_h_is_not_version_1_2_41beta04;