PR libstdc++/33203
* configure.host (error_constants_dir): New variable,
defaulting to os/generic.
( mingw32*): Overide default.
* configure.ac (ERROR_CONSTANTS_SRCDIR): New.
* configure: Regenerate.
* include/Makefile.am (host_headers): Add
$(ERROR_CONSTANTS_SRCDIR)/error_constants.h .
* include/Makefile.in: Regenerate.
* include/std/system_error (enum posix_errno): Remove.
Include <bits/error_constants.h> instead.
* config/os/mingw32/error_constants.h: New.
* config/os/generic/error_constants.h: New.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@128228 138bc75d-0d04-0410-961f-82ee72b054a4