MINOR: trace: Add a set of macros to trace events if HA is compiled with debug

The macros DBG_TRACE_*() can be used instead of existing trace macros to emit
trace messages in debug mode only, ie, when HAProxy is compiled with DEBUG_FULL
or DEBUG_DEV. Otherwise, these macros do nothing. So it is possible to add
traces for development purpose without impacting performance of production
instances.
1 file changed