Empty arguments can be passed to macros per C99 and C++11 specs, which
can then be forwarded to other macros.

Visual Studio's compiler has a bug in the following situation:

    #define A(x) #x
    #define B(x, y) A(x)
    B(, b)

In the above case, Visual Studio first expands x to nothing, then
complains that A is not invoked with the right amount of arguments.
However, x in A(x) is still one argument, even if it expands to no
preprocessing tokens.  See also https://stackoverflow.com/a/7674214.