Feature: ELIF keyword

[MiranDMC]

Please introduce ELIF keyword, so switch-like codes:

if
	0@ == 1
then
	print_help 'ONE'
else
	if
		0@ == 2
	then
		print_help 'TWO'
	else
		if
			0@ == 2
		then
			print_help 'THREE'
		else
			print_help 'OTHER'
		end
	end
end

can be simplified to:

if
	0@ == 1
then
	print_help 'ONE'
elif
	0@ == 2
then
	print_help 'TWO'
elif
	0@ == 3
then
	print_help 'THREE'
else
	print_help 'OTHER'
end

[x87]

I think it's a duplicate of #160

[x87]

I think I prefer else if syntax more, so closing this ticket in favor of #160