fix various descriptions of "ctime"
(closes SF patch #870287)
diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index 211d194..a61e97c 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -909,7 +909,8 @@
\member{st_atime} (time of most recent access),
\member{st_mtime} (time of most recent content modification),
\member{st_ctime}
-(time of most recent content modification or metadata change).
+(platform dependent; time of most recent metadata change on \UNIX, or
+the time of creation on Windows).
\versionchanged [If \function{stat_float_times} returns true, the time
values are floats, measuring seconds. Fractions of a second may be