r24525: Add output of synonym information to show_parameter_list().

r24525: Add output of synonym information to show_parameter_list().
Also simplify lp_canonicalize_parameter by making use of
the new function "is_synonym_of".

Michael

Note: If anything depends on the exact former output format of
show_parameter list, I would trigger the output of synonym information
by a boolean verbose switch (that could be passed to testparm
via the "-v" command line switch).