r335: added much better handling of servers that die unexpectedly during a

r335: added much better handling of servers that die unexpectedly during a
request (a dead socket). I discovered this when testing against Sun's
PC-NetLink.

cleaned up the naming of some of the samr requests

add IDL and test code for samr_QueryGroupMember(),
samr_SetMemberAttributesOfGroup() and samr_Shutdown().  (actually, I
didn't leave the samr_Shutdown() test in, as its fatal to windows
servers due to doing exactly what it says it does).
(This used to be commit 925bc2622c105dee4ffff809c6c35cd209a839f8)