CORE::require was always parsed as require().

CORE::require was always parsed as require().
That's because require() isn't overridable at tokenizer-level
like other overridable built-ins, but is handled by the optree
builder. So, find a way to pass the information that require()
was written as CORE::require() to Perl_ck_require. This is
done by adding a new token type REQUIRE and by adding OPf_SPECIAL
to OP_REQUIRE when it's saw as CORE::require in the program text.
This fixes bug [perl #37274] The "CORE" in CORE::require is ignored.

p4raw-id: //depot/perl@25599