* systty.h: Remove code for Aix on 386, unsupported platform.

* systty.h: Remove code for Aix on 386, unsupported platform.

* s/ms-w32.h: Remove boilerplate comments.
(fcloseall, fgetchar, flushall, fputchar, getw, putw): Remove, unused.

* s/gnu-linux.h (TERM): Remove support.
(HAVE_SYSVIPC): Remove, unused.
(A_TEXT_OFFSET, A_TEXT_SEEK, ADJUST_EXEC_HEADER): Remove, not used
for this system.

* process.c: Remove support for IRIS, unused.
Remove support for TERM, not relevant anymore.

* unexalpha.c (DEFAULT_ENTRY_ADDRESS): Remove, replace the only
used with the definition.

* s/aix4-2.h (static): Do not undef.

* m/ibmrs6000.h: Remove code depending on USG5_4, this file is
only used on Aix.
(HAVE_SYSVIPC): Remove, unused.

* m/hp800.h (CANNOT_DUMP): Do not undef.

* m/alpha.h: Fix comment.

* s/usg5-4.h (HAVE_SYSVIPC): Remove, unused.
(USG_SHARED_LIBRARIES): Remove, only used in unexec.c which is not
used by this configuration.
* emacs.c: Remove code depending on USG_SHARED_LIBRARIES.
* unexec.c: Remove code depending on HPUX and
USG_SHARED_LIBRARIES, not used with this file.  Remove code
depending on IRIS, unused.  Remove if 0-ed code.