add __attribute__((noreturn)) to suppress a waring

I found the following warning with Fedora 14 / gcc 4.5.1.
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pg_backup_archiver.c: In function ‘_discoverArchiveFormat’:
pg_backup_archiver.c:1736:11: warning: ‘fh’ may be used uninitialized
in this function
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To suppress it, I'm thinking to add noreturn to die_horribly().
Any objections?  Another solution might be adding a dummy assignment
after calls of die_horribly().

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Itagaki Takahiro