Reverse Defer

Defer efuns executes functions in lifo mode (The last function that i added with defer efun, is executed first)

I think that execute those functions in fifo mode will be useful, so i've modified this efun for this purpose.

I added defined REVERSE_DEFER in options.h for compatibility with original efun. My english is very bad, if you accept this change, could you write a good comment in this define, please?

I've wrote defer efun tests in testsuite too.

I hope this change it's useful. If don't, no matter!

PD:Sorry my english!