CSV BOM-strip clashes with double-quoted header line: "unwrapped double quote at line 0"

[johnkerl]

https://github.com/johnkerl/miller/releases/tag/v5.2.0 introduced stripping for the CSV BOM (leading 0xef 0xbb 0xbf). However, it incorrectly handles the case when the header line itself contains double quotes:

$ cat 1.csv
a,b,c
"1","2","3"
"1","2","3"

$ cat 2.csv
"a","b","c"
"1","2","3"
"1","2","3"

$ hex 1.csv
00000000: ef bb bf 61  2c 62 2c 63  0a 22 31 22  2c 22 32 22 |...a,b,c."1","2"|
00000010: 2c 22 33 22  0a 22 31 22  2c 22 32 22  2c 22 33 22 |,"3"."1","2","3"|
00000020: 0a                                                 |.|
$ hex 2.csv
00000000: ef bb bf 22  61 22 2c 22  62 22 2c 22  63 22 0a 22 |..."a","b","c"."|
00000010: 31 22 2c 22  32 22 2c 22  33 22 0a 22  31 22 2c 22 |1","2","3"."1","|
00000020: 32 22 2c 22  33 22 0a                              |2","3".|

$ mlr --csv cat 1.csv
a,b,c
1,2,3
1,2,3
$ mlr --csv cat 2.csv
mlr: syntax error: unwrapped double quote at line 0.

[johnkerl]

Fixed by 7d19697