Faster wp_clone function

[sambauers]

The current wp_clone() function calls version_compare() on every execution, which is slooow.

Attached patch stores the result of version_compare() as a static variable. The speedup for bbPress was about 5% on a large site, not profiled in WordPress yet, but result should be similar as wp_clone() is called in cache retrieval processes.

[jacobsantos]

Um, isn't $can_static already set? I usually just use is_null().

[ryan]

(In [10350]) Run version_compare only once for wp_clone(). Props sambauers. fixes #8844 for trunk

[ryan]

(In [10351]) Run version_compare only once for wp_clone(). Props sambauers. fixes #8844 for 2.7

[sambauers]

Fix for syntax errors in PHP4 attached.

[azaozz]

(In [10353]) Faster wp_clone function fix, props sambauers, fixes #8844 for trunk

[azaozz]

(In [10354]) Faster wp_clone function fix, props sambauers, fixes #8844 for 2.7