* libguile/eval.c (s_macro_keyword): New static identifier.

	* libguile/eval.c (s_macro_keyword): New static identifier.

	(scm_m_define): Change order to first create binding and
	evaluating the expression afterwards.

	(scm_m_set_x): Memoize complete set! expression.  Only leave
	symbols if no binding exists at memoization time.  Throw error if
	assigning to a syntactic keyword.

	(lazy_memoize_variable): New function.

	(CEVAL): When execution set!, perform lazy memoization if
	unmemoized symbol is detected.

	* libguile/modules.c (module_variable): Return variables with
	unbound value.

	* libguile/tags.h: Fix comment.

	* test-suite/tests/syntax.test: Add test case to check the correct
	handling of define expressions.