since that is the only file we're reading in this function.
For some unkonwn reason, opening mail.sdt can sometimes take as long
as 2-3 seconds when the file is on a SMB/CIFS share. This could cause calls to
getmail() to stall noticeably (e.g. sbbsctrl, with the Statistics windows
visible) and logging into the terminal server or viewing user statistics. This
is a new problem, perhaps only with Vertrauen, but this optimization helps
to eliviate the most obvious performance problems triggered by it.
Better/safer string modification (e.g. use of SAFEPRINTF).

I've likely broken something though, so if you see weird behaviour with
extended ASCII, let me know please.

inserting (long) typedefs to prevent warnings, but in the case of the JS File()
class, actually supporting file lengths > 32-bit.

getlasgmsg() needs a uin32_t* as the second arg.
loadmail() needs an int32_t* as the second argument.
loadposts() needs an int32_t as the first argument.

loadmail() change which had a trickle-up effect to the higher level functions
that use loadmail().

smb_read() will now retry the read operation if the read fails with an errno of
DEADLOCK (occurs on Unix if a Win32 system has the bytes already locked).