remove empty srfi-4, srfi-13, and srfi-14 shlibs

remove empty srfi-4, srfi-13, and srfi-14 shlibs

* srfi/srfi-13.c:
* srfi/srfi-13.h:
* srfi/srfi-14.c:
* srfi/srfi-14.h:
* srfi/srfi-4.c:
* srfi/srfi-4.h:
* srfi/Makefile.am:
* configure.ac: Remove empty shlibs and headers for srfis 4, 13, and
  14. The "version" was never programmatically exported, so there's no
  possible way people could have used these.