Refactor: libcrmcommon: Drop XML_PARSER_DEBUG constant

It clutters the code without much benefit.

Tracing is disabled by default and is highly configurable, so a
compile-time constant isn't really useful. Individual messages can be
kept or dropped according to usefulness, and can be turned on or off in
various ways.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>