cpplib: kill dead code

[Dave Brolley]

I don't see any problems with this patch...

Dave

Zack Weinberg wrote:
> 
> This patch deletes a bunch of code that had been #if-ed out since
> forever.  These are mostly the last vestiges of the old,
> never-finished precompiled header scheme, and support for -lint mode.
> 
> zw
> 
>         * cpperror.c: Remove #ifdef EMACS block.
>         * cppmain.c: Likewise.
>         * cpphash.c: Remove #if 0 blocks.
>         * cppinit.c: Remove #if 0 blocks, and the -lint option.
>         * cpplib.c: Remove #if 0 blocks and code referencing
>         pcp_inside_if or for_lint.  Remove duplicate error message.
>         Fix error messages for #else after #else or #elif.  Reformat.
>         Remove archaic TODO list.
>         * cpplib.h: Remove pcp_inside_if and for_lint flags.