read.table() errors with tab as separator (PR#9061)

John.Maindonald at anu.edu.au writes:

(1) read.table(), with sep="\t", identifies 13 our of 1400 records,
in a file with 1400 records of 3 fields each, as having only 2 fields.
This happens under version 2.3.1 for Windows as well as with
R 2.3.1 for Mac OS X, and with R-devel under Mac OS X.
[R version 2.4.0 Under development (unstable) (2006-07-03 r38478)]

(2) Using read.table() with sep="\t", the first 1569 records only
of a 1821 record file are input.  The file has exactly two fields
in each record, and the minimum length of the second field is
1 character.  If however I extract lines 1561 to 1650 from the
file (the file "short.txt" below), all 90 lines are input.

Notice that the single quote is a quote character in read.table (as
opposed to read.delim, which uses only the double quote, to cater for
TAB-separated files from Excel & friends).

[1] "865\tlinear model (lm)! Cook's distance\t152"

                                  ^
                                !!!!

(This reminds me that we probably should shift the default for
comment.char too since it leads to similar issues, but it seems not to
be the problem in this case.)