Do not include <config.h> or <sys/types.h>.

Do not include <config.h> or <sys/types.h>.
Include <stddef.h> instead, since it's all we need for size_t.
(PARAMS): Remove.  All uses removed.
(ARRAY_CARDINALITY): Do not bother to #undef.
(ARRAY_CARDINALITY, ARGMATCH, ARGCASEMATCH, invalid_arg,
ARGMATCH_VALID, XARGMATCH, XARGCASEMATCH):
Remove unnecessary parentheses.
(ARGMATCH_VALID, XARGMATCH, XARGCASEMATCH):
Insert necessary parentheses.
(ARGMATCH_CONSTRAINT, ARGMATCH_VERIFY): New macros.
(ARGMATCH_ASSERT): Use ARGMATCH_CONSTRAINT.