Add a fast path for bitwise-and of two immediate numbers for a 0.7% improvement in SunSpider (4% bitop improvement).

Reviewed by Sam.

This only improves bitwise-and performance, as the additional logic required
for similar code paths on or, xor, and shifting requires additional operations
and branches that negate (and in certain cases, regress) any advantage we might
otherwise receive.

This improves performance on all bitop tests, the cryptography tests, as well as
the string-base64 and string-unpack-code tests.  No significant degradation on
any other tests.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@27615 268f45cc-cd09-0410-ab3c-d52691b4dbfc