move db.h to the end of the includes, make compat.h work better

move db.h to the end of the includes, make compat.h work better

SCCS-vsn: lib/libc/db/btree/bt_close.c 5.9
SCCS-vsn: lib/libc/db/btree/bt_conv.c 5.6
SCCS-vsn: lib/libc/db/btree/bt_debug.c 5.6
SCCS-vsn: lib/libc/db/btree/bt_delete.c 5.7
SCCS-vsn: lib/libc/db/btree/bt_get.c 5.7
SCCS-vsn: lib/libc/db/btree/bt_open.c 5.24
SCCS-vsn: lib/libc/db/btree/bt_overflow.c 5.7
SCCS-vsn: lib/libc/db/btree/bt_page.c 5.3
SCCS-vsn: lib/libc/db/btree/bt_put.c 5.12
SCCS-vsn: lib/libc/db/btree/bt_search.c 5.8
SCCS-vsn: lib/libc/db/btree/bt_seq.c 5.8
SCCS-vsn: lib/libc/db/btree/bt_split.c 5.11
SCCS-vsn: lib/libc/db/btree/bt_stack.c 5.4
SCCS-vsn: lib/libc/db/btree/bt_utils.c 5.9
SCCS-vsn: lib/libc/db/db/db.c 5.4
SCCS-vsn: lib/libc/db/hash/hash.c 5.31
SCCS-vsn: lib/libc/db/hash/hash_bigkey.c 5.9
SCCS-vsn: lib/libc/db/hash/hash_buf.c 5.12
SCCS-vsn: lib/libc/db/hash/hash_func.c 5.4
SCCS-vsn: lib/libc/db/hash/hash_page.c 5.24
SCCS-vsn: lib/libc/db/hash/hsearch.c 5.8
SCCS-vsn: lib/libc/db/hash/ndbm.c 5.13
SCCS-vsn: lib/libc/db/mpool/mpool.c 5.4
SCCS-vsn: lib/libc/db/recno/rec_close.c 5.8
SCCS-vsn: lib/libc/db/recno/rec_delete.c 5.5
SCCS-vsn: lib/libc/db/recno/rec_get.c 5.5
SCCS-vsn: lib/libc/db/recno/rec_open.c 5.13
SCCS-vsn: lib/libc/db/recno/rec_put.c 5.8
SCCS-vsn: lib/libc/db/recno/rec_search.c 5.7
SCCS-vsn: lib/libc/db/recno/rec_seq.c 5.6
SCCS-vsn: lib/libc/db/recno/rec_utils.c 5.6