Re: gthr.h: Use include <> instead of include ""

[Loren James Rittle <rittle at latour dot rsch dot comm dot mot dot com>]

> gthr.h uses #include "...".  IMO system include files should only
> search in system paths and we should therefore use #include <...> to
> avoid including user level files.

Yes, the gcc/gthr*.h files are a tricky beast.  libstdc++ is the first
support library to actually install them for use when the user runs
the related compiler.  When other libraries build against those header
files (e.g. libobjc), they are used only at library construction time
before installation.  However, as you know, C++ libraries are usually
a mix of header files and compiled library code thus existing
approaches didn't work (in light of the presumed existing requirement
that people that configure the library with no threading support must
not pay overhead costs).

> Unfortunatly the appended patch does not work, bootstrapping of GCC
> fails for me with this:

[Your patch actually breaks the fragile staging process mentioned
 below.  Were you seeing an actual bootstrap failure before your
 patch?]

There are already staging rules in libstdc++/acinclude.m4 (see
GLIBCPP_ENABLE_THREADS).  I think Carlo explained this part of it
well.  If you think <> should be used in place of "", then that is the
correct place to make a change.

During the discussion of libstdc++/3243 , someone (Carlo?) mentioned
that it might be wise to convert the "" to <> but it wasn't done.

I think a patch to libstdc++/acinclude.m4 for mainline would be
accepted to fix this.

Regards,
Loren