fread "improperly" parses MS Excel Mac-style .csv

[MPagel]

This bug is really a bug in Microsoft Excel, but manifests as a "bug" in fread.
This bug is related to Issues #2542, #2248, #1183

# Summary of Issue
When saving a CSV as a mac-type in MS Excel Office 2016 from a Windows10 PC, Excel creates a file that has \r after every line EXCEPT the final line, which ends as \r\n. fread then interprets each "line" as a separate column.

# Minimal reproducible example

You may be able to skip many of these file creation steps...taking a well-formed csv or xls file and saving it as mac-type csv is the most critical step.

Create the following in a notepad application and save as input.csv

Col1,Col2
1,data1
2,data2
3,data3

Open input.csv in Excel (2016 used...but likely applies to other versions)
File->Save As->Save as type: Excel Workbook (*.xlsx)->intermed.xlsx
Close Excel

Open intermed.xlsx in Excel
File->Save As->Save as type: CSV (Macintosh) (*.csv)->final.csv
Close Excel

In R...

fread("final.csv")

3,data3ata.table (0 rows and 5 cols): Col1,Col2

fredT<-fread("final.csv",header=T)
dim(fredT)

[1] 0 5

fredF <-fread("final.csv",header=F)
dim(fredF)

[1] 1 5

fredF

V1      V2       V3       V4    V5

1: Col1 Col2\r1 data1\r2 data2\r3 data3

# Output of sessionInfo()
sessioninfo::platform_info()

setting value
version R version 3.5.0 (2018-04-23)
os Windows 8.1 x64
system x86_64, mingw32
ui RStudio
language (EN)
collate English_United States.1252
ctype English_United States.1252
tz America/Los_Angeles
date 2020-01-17

packageVersion("data.table")

[1] ‘1.12.2’