scanner: allow #defines to expand to other #defines
While this would generate a proper symbol for LALA_THREE:
enum { LALA_ONE=1, LALA_TWO=2 };
#define LALA_THREE (LALA_ONE + LALA_TWO)
This would not:
#define LALA_ONE 1
#define LALA_TWO 2
#define LALA_THREE (LALA_ONE + LALA_TWO)
No reason for that. Let's insert the defines into const table just like we do for enums.
The test is the same as in !366 (merged)