When a fatal signal is received, we now write a message to the log
that looks like this:
F/libc ( 1540): Fatal signal 11 (SIGSEGV) at 0xdeadd00d (code=1)
This is useful for debugging fatal signals that turn out not to be
fatal. This also changes the signal reset from SIG_IGN to SIG_DFL,
so that future non-fatal fatal signals are fatal.
The code that blocked SIGUSR1 to avoid being interrupted by the GC
has been removed.
Also, fix minor issues in format_buffer().
Bug 5035703
Change-Id: I8940af47297b5dcf3cf33537e3483ca5334ed565
