src/: Abolish the distinction between different kinds of initializers.

src/: Abolish the distinction between different kinds of initializers.

It made parsing difficult, both because the kind and value needed to be
carted about together, and just technically because of `scan-c-fragment'
interacts badly with token-level lookahead.

Against that, the formatting benefits are very slim, and more so when
one considers that there are ugly `#line' markers around the value
fragment.

So, the distinction is gone; there are no more `value-kind' slots or
arguments; and the `value-form' is now just plain `value'.

This is a fairly straightforward change (except for the radical
simplification of the `parse-initializer' function, which hardly needs
to exist any more), but somewhat far-reaching.