this makes eina_log give bt's for all error logs. this is very useful
in finding just where a problem happens. the problem int he past is
that these have not been too useful due to backtrace_symbols() being
"useless". thus use the eina_btlog tool i added too.
also started infra for a debug monitor that can use the backtrace
infra to collect runtime stats ANY TIME for a process (don't need to
run under a debugger).
@feat