EXPORT_SYMBOL(cred_cachep) credentials patch

Hi Bill and others,

I tried patching kernel 2.4.19-pre10 with both the futex and
credentials patches. The futex patch applies cleanly (except for the
thread-exit part, of course), but the credentials patch requires some
manual intervention in fs/dnotify.c and kernel/sys.c. Nothing fancy,
just lines that have the context changed too much.

However, lockd uses cred_cachep and can be built as a module. But
cred_cachep is not exported.

Easy fix:
1. add 'EXPORT_SYMBOL(cred_cachep);' to kernel/fork.c
2. add fork.o to the export-objs line of kernel/Makefile

Bye,
        Marijn