Sorry for the long title

When a #define references a function-like macro, and passes values to it, the values need to be expanded before they're passed to the function. This mostly affects concatenation operator.

This behavior is different on calls from other statements which are not #defines.

#define concat(x,y) x ## y
#define xconcat(x,y) concat(x,y)

#define NUM 42
int foo1 = concat(0x, NUM); // should be expanded as 0xNUM, which of course won't compile
int foo2 = xconcat(0x, NUM); // should be expanded as 0x42