[OpenAFS] compile error with 1.5.74 on kernel 2.6.28.10

[Adam Megacz]

This is using openafs_1.5.74.1-1.dsc (Debian).  I can probably kludge my
way around it, but I figured in the run-up to 1.6 y'all would like to
know about it.

  - a

  CC [M]  /usr/src/modules/openafs/src/libafs/MODLOAD-2.6.28.10gentzen-SP/osi_gcpags.o
/usr/src/modules/openafs/src/libafs/MODLOAD-2.6.28.10gentzen-SP/osi_gcpags.c: In function 'afs_osi_proc2cred':
/usr/src/modules/openafs/src/libafs/MODLOAD-2.6.28.10gentzen-SP/osi_gcpags.c:111: error: implicit declaration of function 'set_cr_group_info'
make[5]: *** [/usr/src/modules/openafs/src/libafs/MODLOAD-2.6.28.10gentzen-SP/osi_gcpags.o] Error 1
make[4]: *** [_module_/usr/src/modules/openafs/src/libafs/MODLOAD-2.6.28.10gentzen-SP] Error 2
make[4]: Leaving directory `/usr/src/linux-2.6.28.10'
make[3]: *** [openafs.ko] Error 2
make[3]: Leaving directory `/usr/src/modules/openafs/src/libafs/MODLOAD-2.6.28.10gentzen-SP'
make[2]: *** [linux_compdirs] Error 2
make[2]: Leaving directory `/usr/src/modules/openafs/src/libafs'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/usr/src/modules/openafs'
make: *** [build-stamp] Error 2