bug#13439: 24.4.50; improvement of describe-variable/pp

[shigeru . fukaya]

Hi,

`describe-variable' is very slow for large objects.
It is mainly because `pp' used in it is slow on that case
(comments say `take an age').

When `pp' is to a buffer, in other words, output stream is a buffer,
current code is as follows:

1) Output the object to a temporary buffer.
2) Convert the buffer contents to a string.
3) Insert the string to an output buffer.

If the insertion is directry from the temporary buffer without
conversion, things go better dramatically.

Regards,
Shigeru