PING: PATCH: Do not clear the DECL_BIT_FIELD flag (prelude to ObjC fix)

[Richard Kenner]

    What kind of performance problems were you thinking of?

Well, DECL_BIT_FIELD means to use bitfield access techniques, which add
code.  If we use them when we don't need to, we generate worse code.

    I suppose the ObjC front-end could be taught to keep separate
    copies of instance variables for super classes lest they get
    side-effected too often, but that is terribly kludgey.

Why not just use a language-specific flag instead of DECL_BIT_FIELD?