Document that CC1_SPEC is included in the spec for cc1plus

[Jeffrey A Law]

  In message < 199910280918.KAA09996@pathia.cygnus.co.uk >you write:
  > Hi Guys,
  > 
  >   Any objection to my commiting the following patch ?
  > 
  > Cheers
  > 	Nick
  > 
  > 
  > Mon Oct 18 21:16:06 1999  Fred Fish  <fnf@be.com>
  > 
  > 	* tm.texi (CC1PLUS_SPEC): Make it clear in the docs that CC1_SPEC is
  > 	used by both cc1 and cc1plus.
OK short term.

What we really want to do is use COMPILER_SPEC for all the generic stuff,
and return CC1_SPEC and friends to being for specific front-ends.

jeff