The @debugtrap opcode only does the block-and-debug thing if the library
has debug features *and* is calling the cycle handler.
Turn off debug support. This is the default build configuration.
Some of the starttrap flag.
Add the debug-on-start option.
Comment out the XML lines by default.
More comments about libxml2.
Comments on debugger.c
Debug "help" command.
More comments.