maint: remove amiga, atari, msdos, nt, os2, vms sub-directories,

maint: remove amiga, atari, msdos, nt, os2, vms sub-directories,

and all files therein.  This was proposed months prior, and no
one objected.
* amiga/Makefile.gcc: Remove file.
* amiga/Makefile.sasc: Likewise.
* amiga/match.a: Likewise.
* amiga/tailor.c: Likewise.
* amiga/utime.h: Likewise.
* atari/Makefile.st: Likewise.
* msdos/Makefile.bor: Likewise.
* msdos/Makefile.djg: Likewise.
* msdos/Makefile.msc: Likewise.
* msdos/doturboc.bat: Likewise.
* msdos/gzip.prj: Likewise.
* msdos/match.asm: Likewise.
* msdos/tailor.c: Likewise.
* nt/Makefile.nt: Likewise.
* os2/Makefile.os2: Likewise.
* os2/gzip.def: Likewise.
* os2/gzip16.def: Likewise.
* vms/Makefile.gcc: Likewise.
* vms/Makefile.mms: Likewise.
* vms/Makefile.vms: Likewise.
* vms/Readme.vms: Likewise.
* vms/gzip.hlp: Likewise.
* vms/makegzip.com: Likewise.
* vms/vms.c: Likewise.
* Makefile.am (EXTRA_DIST): Remove those file names.