Experimental support for buffering limits in trafficserver
engine: Add ib_config_registered_directives() to get a list of all registered directives.
modules/abort.c: Strip whitespace.
modules/(abort|lua_runtime).c: Include order.
modules/txdump.c: Indentation fix.
modules/(abort|txvars).c: Spell check.
core logger: Traffic Server clears the core log writer (and all writers) before adding its own.

There are changes to the core modules treatment of logging to support
this, being to not re-add the core module's writer and to no clear the
writers as the Traffic Server plugin is doing.
dso: Export symbols loaded from modules by default.  Needed to load lua C extensions, etc.
error_page: Add unit test for relative filename.