new program: timeout

new program: timeout

* AUTHORS: Register as the author.
* NEWS: Mention this change.
* README: Add timeout command to list.
* src/timeout.c: New file.
* src/kill.c (operand2sig): Move function to its own file,
now that timeout.c will also use it.
* src/operand2sig.c (operand2sig): New file, extracted from kill.c.
* src/operand2sig.h (operand2sig): Declare.
* src/Makefile.am (EXTRA_PROGRAMS): Add timeout.
* src/.gitignore: Add timeout binary to list to ignore.
* doc/coreutils.texi (timeout invocation): Add timeout info.
(Signal specifications): New section, also referenced by kill.
* man/Makefile.am (timeout.1): Add dependency.
* man/timeout.x: New file.
* po/POTFILES.in: Add timeout.c and operand2sig.c to list to translate.
* tests/Makefile.am (TESTS): Add the two new tests.
* tests/misc/help-version: Add support for new timeout command.
* tests/misc/invalid-opt: Add support for new timeout command.
* tests/misc/timeout: New file: check basic timeout operation.
* tests/misc/timeout-parameters: New file: check invalid parameter
combinations.