Break android_set_abort_message out of libc_logging.

libc_logging is getting statically linked into the crash handler
library, resulting in two copies of the abort message code existing in
processes, one in the linker, and one in the crash handler.

Move android_set_abort_message to its own file to solve this.

Bug: http://b/36862204
Test: /data/nativetest/debuggerd_test/debuggerd_test32
Change-Id: Ie198c5a3bb07645aa43296915c9a6752693f14a9