[MP3 ENCODER] new countbit routine

[Takehiro Tominaga]

I merged a new code of huffman coding routine into lame 3.36 from
my snapshot. ... Oh, lame 3.37 is out... but no problem. This code
is also avalable for 3.37beta and 3.50.

The new code will produce the completely same file that the older
code did. But about 3% faster than on my celeron464MHz linuxbox.

Please test below patch.
---
Takehiro TOMINAGA // may the source be with you!

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