Allow semicolon ";" at the end

[linwaytin]

First, thank you for this fantastic package.
Maxima is a great symbolic algebra system and it's nice that julia can interact with it.

For now the expression from julia side does not allow semicolon ";" at the end.
For example, mcall(m"1+2;") will return error.
Although mcall(m"1+2") is natural, multi-line expressions like

mcall(m"
1+2;
3*4
")

seem weird.

I think the problem is related to the split function in mexpr.jl.
In particular, I found

mex = MExpr("1+2;3^4")
split(mex).str 
#2-element Array{String,1}:
# "1+2"
# "1+2"

The following seems strange to me.

Maxima.jl/src/mexpr.jl

Lines 136 to 138 in 7be4dbd

	for j in 1:length(p)
	push!(n, p[i])
	end

I am wondering if it should be p[j] instead of p[i].