Fix HUD frags count refresh with the software renderer if self-frags count changes

The classic frag bar always showed the difference ps->frag - ps->fraggedself, while the status bar showed max(ps->frag - ps->fraggedself, 0).

What was wrong was that the refreshes specific to software rendering were done based on the ps->frag value alone.

Another option is to always refresh the values (as done for the new frag list). Conditional refresh was obviously more important for 90s-era PCs.