pgsql: Fix another longstanding problem in copy_relation_data: it was

Log Message:
-----------
Fix another longstanding problem in copy_relation_data: it was blithely
assuming that a local char[] array would be aligned on at least a word
boundary.  There are architectures on which that is pretty much guaranteed to
NOT be the case ... and those arches also don't like non-aligned memory
accesses, meaning that log_newpage() would crash if it ever got invoked.
Even on Intel-ish machines there's a potential for a large performance penalty
from doing I/O to an inadequately aligned buffer.  So palloc it instead.

Backpatch to 8.0 --- 7.4 doesn't have this code.

Tags:
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REL8_3_STABLE

Modified Files:
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    pgsql/src/backend/commands:
        tablecmds.c (r1.242.2.6 -> r1.242.2.7)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c?r1=1.242.2.6&r2=1.242.2.7)