Make sure that adb_poll sets revents for all of the structs passed in.
Also, zero initialize all of the adb_pollfd structs in the tests.
Change-Id: Ia639679a7e6f77483655f1552e89081c4673aa87
Windows restricts the return value of threads to 32-bits, even on 64-bit
platforms. Since we don't actually return meaningful values from thread,
resolve this inconsistency with POSIX by making adb's thread abstraction
only take void functions.
Change-Id: I5c23b4432314f13bf16d606fd5e6b6b7b6ef98b5