Add timed versions of stack dumping functions.

Under some unknown circumstances, debuggerd could become unresponsive.
If you try and take a bugreport during this time, it will hang forever.
Adding functions that have a timeout will allow dumpstate to stop if
dumping is taking too long.

Bug: 18766581
Change-Id: I85053b8dcfe6224e2b64b4d8f7f2ef448b3cda34