Duke3D: Add projectile WORKSLIKE flag PROJECTILE_BLAST_CUMULATIVE
This flag alters the radiusdamage calculation such that the blast damage is added cumulatively to the current htextra of the actor, rather than overwriting the current applied damage completely.
In particular, this allows the projectile to apply both impact and blast damage.
MR Notes: I expect
PROJECTILE_PENETRATE to be backported from NetDuke32 eventually, hence I used flag
0x01000000 for this one.
I was also thinking about maybe having a global flag that enables cumulative blast damage for every radiusdamage calculation, including the hardcoded ones. This would obviously break default Duke3D if enabled, but it might be something useful for Total Conversions.