r287797 breaks build WITHOUT_NIS

[Justin Hibbits]

When building WITHOUT_NIS, the following errors show up (base gcc, for
building powerpc):

cc1: warnings being treated as errors
/home/chmeee/freebsd/head/lib/libc/gen/getgrent.c: In function
'compat_setgrent':
/home/chmeee/freebsd/head/lib/libc/gen/getgrent.c:1258: warning:
comparison is always false due to limited range of data type
/home/chmeee/freebsd/head/lib/libc/gen/getgrent.c:1267: warning:
comparison is always false due to limited range of data type
/home/chmeee/freebsd/head/lib/libc/gen/getgrent.c: In function 'compat_group':
/home/chmeee/freebsd/head/lib/libc/gen/getgrent.c:1355: warning:
comparison is always false due to limited range of data type
/home/chmeee/freebsd/head/lib/libc/gen/getgrent.c:1378: warning:
comparison is always false due to limited range of data type

Converting the local variable in the macros back to int fixes it.

- Justin