Changes in PAPPL

Changes in v1.3b1

Added timer APIs to manage periodic tasks (Issue #208)
Added debug logging for device management.
Fixed a device race condition with job processing.
Fixed a potential value overflow when reading SNMP OIDs (Issue #210)
Fixed more CUPS 2.2.x compatibility issues (Issue #212)
Fixed a 100% CPU usage bug when cleaning the job history (Issue #218)
Fixed the default values of --with-papplstatedir and --with-papplsockdir to use the localstatedir value (Issue #219)
Fixed a initialization timing issue with USB gadgets on newer Linux kernels.
Updated PAPPL to conform to the new prototype PWG 5100.13 specification (Issue #216)