Added proper "need 'this' to access member foo" errors instead of "variable foo not resolved" for some cases, added FIXME for the old error! Added a bit more information to the runtime's cyclic dependency detection exception.

module bug80;
extern(C) int printf(char*, ...);

void main()
{
    byte b = 10;
    int i = b += 2;
    printf("byte=%d int=%d\n", b, i);
    assert(b == 12);
    assert(i == 12);
}