outmacho.c: stylistic cleanups
outmacho.c: stylistic cleanups

- No need to cast (int32_t)NULL for a sentinel; just write 0.
- Fix weird formatting of a structure.
- Remove redundant parantheses.

projedi/nasm,letolabs/nasm,Distrotech/nasm,projedi/nasm,turingstudio/nasm,turingstudio/nasm,letolabs/nasm,turingstudio/nasm,Distrotech/nasm,techkey/nasm,turingstudio/nasm,techkey/nasm,techkey/nasm,projedi/nasm,projedi/nasm,techkey/nasm,techkey/nasm,Distrotech/nasm,Distrotech/nasm,letolabs/nasm,projedi/nasm