Introduce new parser token PU_identifier
Summary:
In order to be able to locally detect calls to PU expression (was
`Class::Field::expr`, now is `Class:Field::expr`), and new parsing rule
is introduced to directly create a `PU_identifier` from the source code.
Previously we where scannin for special `Class_const(Class_const _)` pattern
to build them _after_ the parsing was done.
Reviewed By: CatherineGasnier
Differential Revision:
D14421012
fbshipit-source-id:
ffb5c5e0ed33e7905dea8addcf3bc427f2ffa775