Clean up abort.

* A dlmalloc usage error shouldn't call abort(3) because we want to
  cause a SIGSEGV by writing the address dlmalloc didn't like to an
  address the kernel won't like, so that debuggerd will dump the
  memory around the address that upset dlmalloc.

* Switch to the simpler FreeBSD/NetBSD style of registering stdio
  cleanup. Hopefully this will let us simplify more of the stdio
  implementation.

* Clear the stdio cleanup handler before we abort because of a dlmalloc
  corruption error. This fixes the reported bug, where we'd hang inside
  dlmalloc because the stdio cleanup reentered dlmalloc.

Bug: 9301265
Change-Id: Ief31b389455d6876e5a68f0f5429567d37277dbc

libc/private/libc_logging.h

@@ -78,6 +78,15 @@ __LIBC_HIDDEN__ void __libc_set_abort_message(const char* msg);
 __LIBC_HIDDEN__ __noreturn void __libc_fatal(const char* format, ...)
     __printflike(1, 2);
 
+//
+// Formats a message to the log (priority 'fatal'), but doesn't abort.
+// Used by the malloc implementation to ensure that debuggerd dumps memory
+// around the bad address.
+//
+
+__LIBC_HIDDEN__ void __libc_fatal_no_abort(const char* format, ...)
+    __printflike(1, 2);
+
 //
 // Formatting routines for the C library's internal debugging.
 // Unlike the usual alternatives, these don't allocate.