adb: increase the FD table size on Win32.

128 maximum FDs is a pretty low limit, which can easily be exhausted by
port forwarding. Bump the maximum up to 2048, and add a test that checks
whether we can actually use a few hundred sockets.

Bug: https://code.google.com/p/android/issues/detail?id=12141
Bug: http://b/28246942
Change-Id: Ia4a2ff776e8e58ec13378756f19d80392679ece9
(cherry picked from commit b31e1710)