used to syslog and also send to stderr).
This behaviour can be changed by setting $LIBC_DIAGASSERT to a
string containing one or more of the following letters:
a abort() after syslog and/or print to stderr
A opposite of a
e print assertion message to stderr
E opposite of e
l log assertion message to syslog
L opposite of l
This allows per-process control of the _DIAGASSERT() behaviour (e.g,
if you want to abort() after the assertion is raised) by modifying the
environment before starting the process.
Note that __DIAGASSERT() is still a no-op unless libc is compiled
with -D_DIAGNOSTIC.
* Implement __assert()/__diagassert() by calling __assert13()/__diagassert13()
with a function of NULL, reducing unnecessary code duplication
