When ASan currently detects a bug, by default it will only print out the text of the report to stderr. This patch changes this behavior and writes the full text of the report to syslog before we terminate the process. It also calls os_trace (Activity Tracing available on OS X and iOS) with a message saying that the report is available in syslog. This is useful, because this message will be shown in the crash log.
For this to work, the patch makes sure we store the full report into error_message_buffer unconditionally, and it also strips out ANSI escape sequences from the report (they are used when producing colored reports).