Fix spurious kassert on interrupted blocking read from /dev/random.

Return EINTR in this case instead.  While here, clarify comment.

Fixes PR kern/48119, simpler than the patch attached there, per
discussion with tls@, who had this right in the earlier version
of rndpseudo.c before I broke it (oops!).
Fix a NULL dereference if the exit_alt_charset_mode capability is not defined.

The previous version of this file changed a terminal initialisation test on
the exit_attribute_mode capability, checking for the exit_alt_charset_mode
capability as a substring, rather than performing a search for the hard-coded
^O character.

That works better on terminals where ^O is not the correct value for
exit_alt_charset_mode.  But it works worse on terminals that don't have a
definition specified for exit_alt_charset_mode.

For example:

% TERMCAP='xterm:me=\E[m:' TERM=xterm vi
segmentation fault (core dumped)  TERMCAP='xterm:me=\E[m:' TERM=xterm vi

The crash can be avoided (without fixing the bug) by defining
exit_alt_charset_mode:

% TERMCAP='xterm|:me=\E[m:ae=:' TERM=xterm vi
ex/vi: Error: xterm: No such process

We now test exit_alt_charset_mode for NULL before continuing with the fatal
test, restoring the original no-crash behaviour.

XXX does_ctrl_o() is now just a naive reimplementation of strstr(), so should
probably just use strstr() instead.
Import dwc2 2013-09-25
Resolve conflicts
Avoid using unmaped PCI registers. From Wolfgang Stukenbrock in
PR kern/48236.
Import Postfix 2.10.2. Major changes since version 2.9.* are:
- Separation of relay policy (with smtpd_relay_restrictions) from spam policy
  (with smtpd_{client, helo, sender, recipient}_restrictions), which makes
  accidental open relay configuration less likely. The default is backwards
  compatible.
- HAproxy load-balancer support for postscreen(8) and smtpd(8). The nginx
  proxy was already supported by Postfix 2.9 smtpd(8), using XCLIENT commands.
- Support for the TLSv1 and TLSv2 protocols, as well as support to turn them
  off if needed for inter-operability.
- Laptop-friendly configuration. By default, Postfix now uses UNIX-domain
  sockets instead of FIFOs, and thus avoids MTIME file system updates on an
  idle mail system.
- Revised postconf(1) command. The "-x" option expands $name in a parameter
  value (both main.cf and master.cf); the "-o name=value" option overrides
  a main.cf parameter setting; and postconf(1) now warns about a $name that
  has no name=value setting.
- Sendmail-style "socketmap" lookup tables.
Resolve conflicts from last import.
Update list of source files after import of Postfix 2.10.2.
Postfix 2.10.2 was imported.
Update list of generated header files.
sess_hash_bucket: convert to murmurhash2, include ports, use random seed.
Give RUMP mutex and rwlock their own cache-line.  Also give a separate
cache-line for the rwlock's reader counter.