fix(codegen): fix immutable function paramiters

[blazejOz]

in FunctionAST::codegen(...)

moved entry for basic block above argument parsing

and added args allocation on stack and into namedValues map

now code like:
fn factorial(int n): int {
int res = 1;
while (n > 1) {
res = res * n;
n = n - 1;
}
return res;
}

works without extra variables.