Use i8* instead of void* for generated LLVM IR

[sampsyo]

It looks like LLVM doesn't like using void* for opaque pointers. Trying to compile some LLVM IR actually gave me a useful hint:

$ /usr/local/Cellar/llvm/4.0.0_1/bin/opt add.ll             
/usr/local/Cellar/llvm/4.0.0_1/bin/opt: add.ll:6:22: error: pointers to void are invalid - use i8* instead
define i32 @main(void*) {

Apparently, at least until opaque pointer types come to LLVM IR, the right type to use for this sort of thing is a pointer to 8-bit integers.

One easy way to do this would be to define a constant for the i8* type (called FUNCTION_ENV_TYPE?) and then use it wherever we currently have llvm.PointerType.create(llvm.VoidType.create(), 0).

[rhenwood39]

Got it! I'll try fixing that within the next day or two a put in a new pull request.

If you remember, I mentioned the other day that there was also a bug where the function environment function pointer was not being initialized properly. So I'll try including the fix for that in my pull request as well.

[sampsyo]

Cool! I'd be happy to take a look at that separately too if it would be helpful.