file_truncate(): provide full "large file" support on Windows, by dropping MS's inadequate _chsize() function. This was inspired by SF patch 498109 ("fileobject truncate support for win32"), which I rejected. libstdtypes.tex: Someone who knows should update the availability blurb. For example, if it's available on Linux, it would be good to say so. test_largefile: Uncommented the file.truncate() tests, and reworked to do more. The old comment about "permission errors" in the truncation tests under Windows was almost certainly due to that the file wasn't open for *write* access at this point, so of course MS wouldn't let you truncate it. I'd be appalled if a Unixish system did. CAUTION: Someone should run this test on Linux (etc) too. The truncation part was commented out before. Note that test_largefile isn't run by default.

--- a/Doc/lib/libstdtypes.tex	Mon Mar 11 00:07:13 2002 +0000
+++ b/Doc/lib/libstdtypes.tex	Mon Mar 11 00:24:00 2002 +0000
@@ -1154,9 +1154,8 @@
 \begin{methoddesc}[file]{truncate}{\optional{size}}
   Truncate the file's size.  If the optional \var{size} argument
   present, the file is truncated to (at most) that size.  The size
-  defaults to the current position.  Availability of this function
-  depends on the operating system version (for example, not all
-  \UNIX{} versions support this operation).
+  defaults to the current position.
+  Availability:  Windows, many \UNIX variants.
 \end{methoddesc}
 
 \begin{methoddesc}[file]{write}{str}