Fix portability breakage in pg_dump.

Commit 0eea8047 introduced some overly
optimistic assumptions about what could be in a local struct variable's
initializer.  (This might in fact be valid code according to C99, but I've
got at least one pre-C99 compiler that falls over on those nonconstant
address expressions.)  There is no reason whatsoever for main()'s workspace
to not be static, so revert long_options[] to a static and make the
DumpOptions struct static as well.