Use nasty clone hacks to let us close random file descriptors to be
able to connect to debuggerd when the fd table is full.
Bug: http://b/32013594
Test: crasher exhaustfd-SIGSEGV
Change-Id: I47772e9a5994da4473bd935b105d9c36827c017a
These were previously required when bionic used tgkill to reraise
signals, but now that we use rt_tgsigqueueinfo to reraise signals, they
are no longer necessary.
Change-Id: I46ba9f14039a727d0a2c4c3a9d93a3532ba8f263