Canonize C subscript expressions

In C, a memory can be accessed using subscript as in memory[index], with memory being some pointer expression and index being some integer type based number, which is transformed to *((memory) + (index)). Contrary to other programming languages, you can also switch the memory and index arguments in the subscript expression, i.e. index[memory], and it evaluates to *((index) + (memory)), which is equal to *((memory) + (index)).

We could canonize these expressions such that the operand of the subscript expression, i.e. the [index] part, is always some integer based number. This could easy CPA implementations relying on these kinds of expressions.