dmd warning request: warn for bitwise OR in conditional

[Ali Çehreli]

We've been bitten by the following bug recently in C code:
    uint flag = 0x1;
    uint flags;

    if (flags | flag) {
        dout.writefln("oops");
    }

The programmer intended &.

It is (almost?) always an error to use | in a conditional. At least the 
conditional in the above code is always true; so dmd could generate a 
warning. (Yes, I used -w.)

Ali