Fix boilerplate comments in btree_gist
Heikki Linnakangas <heikki.linnakangas@iki.fi>
Fix boilerplate comments in btree_gist A few of these were copy-pasted wrong, like the comment "Bytea ops" in btree_numeric.c. Instead of fixing the incorrect ones, replace them all with generic comment "GiST support functions". Also tidy up the inconsistent newlines between various functions while we're at it.