Fix comparison of array types

Currently it's not possible to call functions if an argument is a
pointer to an array:
```
(gdb) l f
1       int f (int (*x)[2])
2       {
3         return x[0][1];
4       }
5
6       int main()
7       {
8         int a[2][2] = {{0, 1}, {2, 3}};
9         return f (a);
10      }
(gdb) p f(a)
Cannot resolve function f to any overloaded instance
```

This happens because types_equal doesn't handle array types, so the
function is never even considered as a possibility.

With array type handling added, by comparing element types and array
bounds, the same works:
```
(gdb) p f(a)
$1 = 1
```

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=15398


Co-Authored-By: Keith Seitz <keiths@redhat.com>
Reviewed-By: Guinevere Larsen <blarsen@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>