Created attachment 178243 [details] [review]
ElementAccess check for valid rank and index access in fixed-size and constant arrays

ElementAccess check for valid rank and index access in fixed-size and constant arrays

Check if we are corrently accessing to a valid rank of an array. For example, 
when you have:
   int[,] array = {{1,2}, {3,4}};
You can't do:
   int i = array[0,1,0];
but vala syntax checker allowed this before, and vala compiler didn't work just 
due a codegen error (it wasn't possible to get the length parameter for the rank 2):

ERROR:valaccodearraymodule.c:942:vala_ccode_array_module_real_get_array_length_cvalue:
assertion failed: (_tmp20_)

So, I've fixed the issue, checking for valid rank access for every array access
(since rank is always known).

Then, in constant arrays and in fixed_length arrays the max item (for each rank)
you can access to is known too, so in the cases where the index is clearly
specified (using an integer literal value), I've added a check to verify if that
value fits in the array range for each array rank.
For example if you have:
    int[,] array = {{1,2}, {3,4}};
Is a non sense doing:
    int i = array[1,5];

Vala didn't checked this before, now it does.