Use gensym-ed variable in @compile and @jit

[jumerckx]

This should fix #237.

[mofeing]

thanks @jumerckx! would you mind adding a test for this? like try compile a function called f or so. the function can do nothing like:

f(x) = x
x = rand(2,2)
y = Reactant.to_rarray(x)
z = @jit f(y)

[jumerckx]

thanks @jumerckx! would you mind adding a test for this? like try compile a function called f or so. the function can do nothing like:

f(x) = x
x = rand(2,2)
y = Reactant.to_rarray(x)
z = @jit f(y)

That example actually doesn't trigger the bug because then it's just shadowing f. It's only when f is used within the function that is compiled that there is a problem.
I checked that the test I added failed before this pr.

f(x) = x
g(x) = f(x)
x = rand(2,2)
y = Reactant.to_rarray(x)
@test (@jit g(y); true)

[mofeing]

great! thanks!