Fixed longstanding bug in the description of strftime's %W code.

Doc/lib/libtime.tex

@@ -232,7 +232,7 @@ specification, and are replaced by the indicated characters in the
   \lineiii{\%w}{Weekday as a decimal number [0(Sunday),6].}{}
   \lineiii{\%W}{Week number of the year (Monday as the first day of the
                 week) as a decimal number [00,53].  All days in a new year
-                preceding the first Sunday are considered to be in week 0.}{}
+                preceding the first Monday are considered to be in week 0.}{}
   \lineiii{\%x}{Locale's appropriate date representation.}{}
   \lineiii{\%X}{Locale's appropriate time representation.}{}
   \lineiii{\%y}{Year without century as a decimal number [00,99].}{}