Add secinfo to the NFS client

These patches will add the secinfo procedure to the NFS client and do some cleanup along the way. The final result will should be able to cross mountpoints using a different form of security and auto-detect the security of an initial NFS v4 mount.

v4:
- Properly set the number of security flavors decoded by the client
- Return an int rather than an rpc_authflavor_t for better error checking
v3:
- Check for server returning too many security flavors
- Check for gss_oid_len > max_gss_oid_len
- New functions in namespace.c should be static

v2:
- Add more details about the call_sync improvement
- Don't initialize global constant function pointers to NULL

Bryan