Dollars in identifiers and DOLLARS_IN_IDENTIFIERS cruft

[Neil Booth <neil at daikokuya dot demon dot co dot uk>]

tm.texi states:-

@item DOLLARS_IN_IDENTIFIERS
Define this macro to control use of the character @samp{$} in
identifier names.  0 means @samp{$} is not allowed by default; 1 means
it is allowed.  1 is the default; there is no need to define this
macro in that case.  This macro controls the compiler proper; it does
not affect the preprocessor.

It says this macro is for the compiler proper, and does not affect
CPP.  The latter is correct - cpplib does not use the macro.  However,
the former is incorrect too!  The compiler front ends have gunk lying
around that uses this macro to set a variable

extern int dollars_in_ident;

, and handlers for "-f{no-,}dollars-in-ident" that set or clear this
variable, but nothing has _really_ used this variable since we moved
to an integrated CPP a year ago.

I can see 3 possibilities here:

1) Remove DOLLARS_IN_IDENT, dollars_in_ident from everything in the
   compiler (leaving -$ for CPP of course).  This will have no effect
   since nothing is effectively using them now.

2) 1), and get cpplib to use DOLLARS_IN_IDENT.  It might be a bug that
   it doesn't at present.

3) Something more serious is wrong, and the compiler should be using the
   variable and macro.

Someone let me know what to do, and I'll send a patch in cases 1) and
2).

Neil.