Add -assets option to specify data.zip (#139)

This is useful for distributions, which may not want to put data.zip in
the same directory as the binary. This can't be distribution-specific
due to the license ("Altered source/binary versions must be plainly
marked as such, and must not be misrepresented as being the original
software.").

desktop_version/src/FileSystemUtils.h

@@ -6,7 +6,7 @@
 
 #include "tinyxml.h"
 
-int FILESYSTEM_init(char *argvZero);
+int FILESYSTEM_init(char *argvZero, char* assetsPath);
 void FILESYSTEM_deinit();
 
 char *FILESYSTEM_getUserSaveDirectory();