from Lawrence D'Oliveiro (ldo)
notes from tracker:
use bool for return type from BLI_remlink_safe, necessitating including BLI_utildefines.h in BLI_listbase.h
get rid of duplicate BLI_insertlink, use BLI_insertlinkafter instead.
A few places which were using BLI_insertlinkafter (actually BLI_insertlink), when it would be simpler to use BLI_insertlinkbefore instead.