modlua: Internal API clean up and fixing a memory leak with Lua module configuration directives.

The memory leak is a use of malloc with no free that has been in our
code for some time. It was recently highlighted by static analysis.

The API clean relates to a boolean "config_time". This magic value has
been renamed to "register_directives" and is now only used for calls to
static functions in lua.c. The renaming more clearly reflects what the
boolean does, which is push a function pointer to register directives or
push NULL as a placeholder.
ib_util_mkpath: Simplify function and remove race condition.
ats-txlog: Removing ats-txlog. Txlog no longer needs to communicate with Traffic Server, so this module should no longer be needed.
ats-txlog: Updating Makefile to match previous commit.
ats-txlog: Neglected to save the last change to Makefile.am. Remove ats-txlog some more.
setvar: When expanding a string value the wrong pointer was being stored.
servers/trafficserver/ironbee.c: Remove code that set a value that was never read.
servers/trafficserver/ironbee.c: Stop storing return value of ib_error_callback() for no purpose.
various: Rename instance_uuid to instance_id (RNS-755)
predicate/tests/Makefile.am: Add subdir-objects to automake options.
automata/bin/trie_generator.cpp: Improve user feedback.
persistence: Comments, formatting, and adding unit tests.
engine/rule_engine.c: Fix bug caused by recent UUID changed. (CID 1150799)
engine/rule_engine.c: Fix memory leak from ib_util_hex_escape() call. (CID 1150800)
example_servers/unparsed_cpp.cpp: Improve exception handling. (CID 1150809, 1150810, 1150811)
persist.c: Printf format error.
various: Whitespace cleanup.
various: Include order cleanup.
modules/txlog_json.cpp: Remove mysterious initial blank line.
various: Spell check.