curl: IMAP literal size truncation on 32-bit platforms corrupts downloads and desynchronizes the response parser

Summary On 32-bit builds of libcurl, the IMAP FETCH handler truncates a server-announced literal size size from curlofft 64-bit to sizet 32-bit when it decides how many already-buffered bytes belong to the literal body. When a malicious or malfunctioning IMAP server announces a literal whose size...