* read.c (scm_read_opts): New opts `elisp-vectors' and

	* read.c (scm_read_opts): New opts `elisp-vectors' and
	`escaped-parens'.
	(s_vector): New.
	(scm_lreadr): Use scm_lreadparen1 instead of scm_lreadparen.  Make
	handling of elisp vector syntax dependent on SCM_ENABLE_ELISP and
	`elisp-vectors' option instead of SCM_ELISP_READ_EXTENSIONS.
	Allow "\(" and "\)" in strings when SCM_ENABLE_ELISP defined and
	`escaped-parens' option set.
	(scm_read_token): If elisp vector syntax active, disallow [ and ]
	in tokens.
	(scm_lreadparen): Rewrite as interface to scm_lreadparen1.
	(scm_lreadparen1): New.

	* read.h: Remove conditionally compiled last arg to
	scm_lreadparen.
	(SCM_ELISP_VECTORS_P, SCM_ESCAPED_PARENS_P): New.