Returns the contents of a given file as a multiline string.
COPY/// file_text_open_read_all(fname)
//
//  Returns the contents of a given file as a multiline
//  string. Lines are delimited by the "#" character.
//  If the file cannot be read, returns undefined.
//
//      fname       file to read, string
//
{
var file = file_text_open_read(argument0);
if (file < 0) return undefined;
var delim = "#";
var str = "";
while (!file_text_eof(file)) {