Revert "Factor out functions responsible for caching I/O routines".

This reverts commit 740e54ca, which seems
to have tickled an optimization bug in gcc 4.5.x, as reported upstream at
https://bugzilla.redhat.com/show_bug.cgi?id=671899
Since this patch had no purpose beyond code beautification, it's not
worth expending a lot of effort to look for another workaround.