Keep a count of bytes read rather than comparing pointers since the
variable_buffer might get reallocated.
Bug and patch by Ken Tossell <ken@tossell.net>
Regression tests by Dmitry Goncharov <dgoncharov@users.sf.net>
Tweaked by Paul Smith <psmith@gnu.org>
* src/function.c (func_file): Use bytes read rather than a pointer.
* tests/scripts/functions/file: Provide various tests for reading
empty files, files with/without newlines, and large files.