* 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
