Remove some more warnings from rx

Remove some more warnings from rx

The mtu variable in InitPeerParams is in the wrong place. It's only
required when the (never used) AFS_USERSPACE_IP_ADDR code is enabled.
Move the variable to the appropriate location, and indent the if and
endif directives in this section to try to make it clearer what the
control flow is (my brain hurt)

Remove the unused rx_pthread_n_event_wakeups variable

ANSIfy rxi_syscall - we can't prototype it yet, sadly.

Reviewed-on: http://gerrit.openafs.org/503
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>