Remove src/s/msdos.h

Remove src/s/msdos.h

* msdos/sed2v2.inp (MSDOS, DOS_NT, FLOAT_CHECK_DOMAIN)
(HAVE_INVERSE_HYPERBOLIC, DEVICE_SEP, IS_DIRECTORY_SEP, IS_ANY_SEP)
(INTERNAL_TERMINAL, NULL_DEVICE, SEPCHAR, USER_FULL_NAME)
(_setjmp, _longjmp): Move here from src/s/msdos.h.
(config_opsysfile, config_machfile): Remove.
* msdos/sed1v2.inp (M_FILE, S_FILE): Remove.
* msdos/mainmake.v2 (TAGS tags): Remove src/s/msdos.h.

* src/s/msdos.h: Remove file.
* src/conf_post.h [MSDOS]: New section, moved from s/msdos.h.
* src/Makefile.in (S_FILE): Remove.
(config_h): Remove S_FILE.