The Prefix transformer had many loops that could be avoided. This
change replaces them for a compiled PCRE regex, taking advantage
of recent PCRE JIT capabilities introduced in PHP.
These changes offer no performance trade-offs, improving lookup
for all categories of prefixes (property/key with shift, ignore
list and fallback to simple rule).
The most affected is the simple rule (no prefix or no conflict
with any kind of prefix rule), yielding the most gains.
