Massive patch

OK, here are the details to the patch I am currently applying.  It
cleans up a lot of the internal tuple access routines.

cvs update and initdb, everyone.

---------------------------------------------------------------------------


heap_fetch requires buffer pointer, must be released
heap_getnext no longer returns buffer pointer, can be gotten from scan
    descriptor
bootstrap can create multi-key indexes
pg_procname index now is multi-key index
oidint2, oidint4, oidname are gone (must be removed from regression tests)
use System Cache rather than sequential scan in many places
heap_modifytuple no longer takes buffer parameter
remove unused buffer parameter in a few other functions
oid8 is not index-able
remove some use of single-character variable names
cleanup Buffer variables usage and scan descriptor looping
cleaned up allocation and freeing of tuples
18k lines of diff

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