Cleaning up more FreeBSDisms from handbook

[Jeremy C. Reed]

I am cleaning up various FreeBSDisms in handbook.

Sorry this is out of context. Please provide thoughts, rewording or fixes
for any of these nine problems (five files) below. (Also the Linux chapter
and ports chapter have many.)

1) doc/en/books/handbook/advanced-networking/chapter.sgml has:

  Bluetooth support is available in &os; 5.0 and newer systems.

and

 BOOT_PXELDR_ALWAYS_SERIAL</literal> (the latter only exists on
 &os; 5.X)

and

 clone_root  ... currently it is only supported on &os; 4.X.

and

 make world ... This method can be applied to either &os; 4.X or 5.X

and

 <literal>device bpf</literal> (<literal>pseudo-device bpf</literal> under
 &os; 4.X) to your kernel

2) doc/en/books/handbook/config/chapter.sgml

 As of &os; 3.1 there is no default
 <filename>/etc/rc.local</filename>;

3) doc/en/books/handbook/disks/chapter.sgml

 The default device is <filename>/dev/acd0</filename> (or
 <filename>/dev/acd0c</filename> under &os; 4.X).

4) doc/en/books/handbook/security/chapter.sgml has

 The <option>kerberos_stash</option> is only available in &os; 4.X.

5) doc/en/books/handbook/multimedia/chapter.sgml

 The Sound Blaster Live is not supported under FreeBSD 4.0
 without a patch ...

 Jeremy C. Reed

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