Be consistent about 'bool'.

Be consistent about 'bool'.

* src/complain.c (warning_issued): Renamed from warn_message_count; now bool.
(complaint_issued): Renamed from complain_message_count; likewise.

* src/main.c (main): Use exit to exit with failure.

* src/complain.c (fatal_at, fatal): Use EXIT_FAILURE and EXIT_SUCCESS
rather than 1 and 0.
* src/main.c (main): Likewise.
* src/getargs.c (getargs): Likewise.
* src/reader.c (reader): Likewise.

* src/getarg.c (getargs): Remove duplicate code for
"Try `bison --help'".

* src/files.c (xfopen, xfclose): Use EXIT_FAILURE rather than 2.
What was that "2" for?

* src/complain.h (fatal, fatal_at): Add __attribute__((__noreturn__)).
* src/getargs.c (usage): Likewise.

* src/getargs.c (getargs): When there are too few operands, report
the last one.  When there are too many, report the first extra
one.  This is how diffutils does it.