Limit value of 64bits FolderSize, DeletedBytes etc. to 50bits value for interoperability with JavaScripy code, because Number value in ECMAScript is "double-precision 64-bit binary format IEEE 754" value.

I don't know how we could seriously limit those values to 50 bits. But my plan is to never allow a folder to grow beyond that size in nsMsg*Store::HasSpaceAvailable as part of increasing the limit in bug 789679. So full 64bit values would be usable internally, however they never get to be used (only up to 50bit). In this bug we could look at other folder types (that are not local), if they are properly limited. However that may not really be possible. If there would be total folder size higher than 50 bits on some server, what can we do? Do we lie to the callers that the size is only 50 bits?

2**50 = 1,125,899,906,842,624 = 1,125,899 GB == 1,125 TB = 1 PB. I don't know pop3 server who supports 1 PB Mbox and IMAP server who supports 1 PB Mbox :-) I don't think Tb iwill be used for mail server on Ultra Super Computer with 1,000,000 nodes with ultra higper switch, with 1,000,000 PB HDD. Even if 1 PB Mbox won't be supported by real server while Tb is alive, code should have 1 PB limit like "current 4GB limit". for safety.