Added printf attribute to buffer_printf, and fixed corresponding type mismatches.
Added printf attribute to link_putfstring, and fixed corresponding type mismatches.
Added printf attribute to send_master_message, and fixed corresponding type mismatches.
Added printf attribute to send_worker_message, and fixed corresponding type mismatches.
Added printf attribute to buffer_format, and fixed corresponding type mismatches.
Added printf attribute to debug, and fixed corresponding type mismatches.
Define __attribute__ if !__GNUC__ or !__clang__.
Casts for varargs in pfs_*
Merge pull request #169 from btovar/dthain-varargs-cleanup

Dthain varargs cleanup