cppinit.c (remove_dup_dir): Add head_ptr argument to handle removal at head.
* cppinit.c (remove_dup_dir): Add head_ptr argument to handle removal
at head.
(remove_dup_nonsys_dirs): New function.
(remove_dup_dirs): Change argument head to head_ptr. Remove warnings.
(merge_include_chains): Remove non-system include directories from
quote and bracket include chains when they duplicate equivalent system
directories.
* doc/cpp.texi (-I): Update.
* doc/cppopts.texi (-I): Update.
* doc/install.texi (--with-local-prefix): Further document usage of
this option.
* doc/invoke.texi (-I): Update.