obexd: Add PBAP cache functions
obexd: Add PBAP cache functions

Add the cache structure and basic functions to handle the cache
entries. This patch breaks temporarily the PBAP core functionalities.

ComputeCycles/bluez,ComputeCycles/bluez,mapfau/bluez,silent-snowman/bluez,silent-snowman/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,pkarasev3/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,pkarasev3/bluez,silent-snowman/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez