* libguile/eval.c (s_expression): Added comment.

	* libguile/eval.c (s_expression): Added comment.

	(s_empty_combination, error_unbound_variable): New static
	identifiers.

	(SCM_VALIDATE_NON_EMPTY_COMBINATION, SCM_EVALIM2, scm_lookupcar1):
	Use ASSERT_SYNTAX, syntax_error or error_unbound_variable to
	signal syntax errors.

	(SCM_CEVAL): Separated handling of evaluator bytecodes and other
	scheme objects.

	* test-suite/tests/syntax.test (exception:missing/extra-expr-misc):
	Removed.

	(exception:illegal-empty-combination): New.

	(exception:missing/extra-expr): Unified capitalization.

	Adapted test for '()' to the new way of error reporting.