uatomic: Specify complete types for atomic function calls

This was unearthed by clang compiler where it complained about parameter
mismatch, gcc doesnt notice this

urcu/uatomic/generic.h:190:10: error: address argument to atomic builtin
must be a pointer to integer or pointer ('void *' invalid)
                return __sync_add_and_fetch_4(addr, val);

Fixed all instances thusly.

[ Edit by Mathieu: use stdint.h types. ]

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>