Remove pointless hackery in melee2.c
Support building with CC=clang

clang doesn't support -fno-strength-reduce (gcc doesn't either, these days, but
it silently ignores it). clang also doesn't support -r (it uses -Wl,-r instead,
which also works with gcc).
Clean up unused definitions.

These are all variables that are defined but not used anywhere in the codebase.
Props to go splint.