cpp.texi: Exclude entire Top node from printed manual.

cpp.texi: Exclude entire Top node from printed manual.

	* doc/cpp.texi: Exclude entire Top node from printed manual.
	Move option index after directive index.  Insert page breaks
	before GFDL and concept index.  Index environment variables
	with command line options.
	* doc/cppenv.texi: Use @vtable for environment variable list.
	Add paragraph explaining semantics of empty elements in path
	variables.  Exclude a cross-reference to Fishkill from the
	manpage.  Remove an unnecessary cross-reference of the entry
	right above the referer.  Don't use @anchor in text that goes
	into manpage.
	* doc/cppopts.texi: Cross-reference the environment variables
	section, not the specific environment variable, for consistency.

From-SVN: r51365