am: learn to process quoted lines that ends with CRLF

In previous changes, mailinfo has learnt to process lines that decoded
from base64 or quoted-printable, and ends with CRLF.

Let's teach "am" that new trick, too.

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-am.txt

@@ -15,6 +15,7 @@ SYNOPSIS
 	 [--whitespace=<option>] [-C<n>] [-p<n>] [--directory=<dir>]
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
+	 [--quoted-cr=<action>]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 
@@ -59,6 +60,9 @@ OPTIONS
 --no-scissors::
 	Ignore scissors lines (see linkgit:git-mailinfo[1]).
 
+--quoted-cr=<action>::
+	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
+
 -m::
 --message-id::
 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),