libstdc++ libtool lossage

[David Edelsohn]

	If you make this change, we need to change gcc.c init_gcc_specs so
that the -shared-libgcc case only links against the gcc_s.  Currently
-shared-libgcc links against both shared and static:

  sprintf (buffer, "%%{shared-libgcc:%s %s}", shared_name, static_name);

This is definitely not what you want and not what you are assuming
-shared-libgcc means.  This also will cause shared libraries to break on
AIX once again.

	FYI, on AIX libtool current builds libstdc++ using

xgcc -shared ... -lgcc_s -lc -lgcc_s -lm -lgcc_s -lc -lgcc_s

libgcc.a never appears implicitly (because of -shared) not explicitly by
libtool.  We need to keep it that way.

David