in C for now.
* rdelim.scm: export the C primitives too.
* documentation.scm: use (ice-9 rdelim).
* filesys.c (scm_link): docstring fix.
* fports.h (scm_setfileno): obsolete declaration removed.
* posix.c: bogus popen declaration removed.
* rdelim.c: new file, split from ioext.c with new proc
scm_init_rdelim.
* rdelim.h: new file.
* Makefile.am: add rdelim.c and related files.
* init.c: call scm_init_rdelim. include rdelim.h.
