Not comma, which is an inconsistency and a mistake probably inherited
from the examples section of RFC1867.
This bug has been present since the day curl started to support
multipart formposts, back in the 90s.
Reported-by: Rob Davies
Bug: http://curl.haxx.se/bug/view.cgi?id=1333
- document the double-quote and backslash need be escaped if quoting.
- libcurl formdata escape double-quote in filename by backslash.
- curl formparse can parse filename both contains '"' and ',' or ';'.
- curl now can uploading file with ',' or ';' in filename.
Bug: http://curl.haxx.se/bug/view.cgi?id=1171