* ice-9.scm (scm-line-incrementors read-line! read-delimited!
read-delimited read-line): moved to rdelim.scm.
scm-line-incrementors is not exported.
* boot-9.scm: import (ice-9 rdelim) for backwards compatibility,
for now.
* lineio.scm: use module (ice-9 rdelim).
* Makefile.am (ice9_sources): add rdelim.scm.
ungetc-char-ready?, since we don't provide that function any
more. The unread-string function doesn't interact properly with
any of the standard I/O functions anyway. (Thanks to Andrew
Archibald.)