preproc.c: allow 64-bit repeat counts
preproc.c: allow 64-bit repeat counts

Allow the count of %rep to exceed 2^31.

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